*3.2. The Effect of Colour on Mood*

#### 3.2.1. Correlation Analysis of Colour and Mood

According to the results of the correlation analysis presented in Figure 4, it can be observed that there are significant correlations among all variables. The correlation coefficients of the scores of all variables were more than 0, except for the negative correlation coefficient of the depression score. So, the anxiety-depression score was negatively correlated with the rest of the hue and lightness scores and positively correlated with the scores of all the remaining variables. For example, the correlation coefficient between the anxiety-depression score and the warm colour score is −0.318 \*\*, which means that they are significantly correlated at the 99% significance level and are negatively correlated. By analogy, this can explain the correlation between all other variables. The higher the anxiety-depression value, the lower is the colour score. The higher the hue score, the higher is the lightness score.

#### 3.2.2. Analysis of the Effect of Colour on Mood

The colours were divided into two parts: hue contrast (neutral, warm, and cold colours) and brightness contrast. The data in Tables 3 and 4 were scored according to three emotional criteria: pleasure, relaxation, and focus, as well as the box plots in Figure 5. According to the sphericity test results, *p*-value is less than 0.05, and the data does not fulfil the sphericity hypothesis. Combined with the results obtained from the multivariate test (*p* = 0.000), it can be found that the results demonstrate a statistically significant difference (*p* < 0.001), indicating that there is a significant difference in the effect of different colour classrooms on mood. This corroborates the validity of H2 at the beginning of this paper.


**Figure 4.** Correlation test among dimensions. Note: More asterisk "\*" imply a stronger correlation. **Table 3.** Colour hue mean and standard deviation.


Note: Options are scored on a 5-point scale, with scores 1–5 corresponding to negative to positive emotions.

As can be observed from Table 3, for the three emotional criteria of pleasure, relaxation, and attention, the subjects' scores all showed with the mean values: warm classroom (WC) > cold classroom (CC) > neutral classroom (NC). This indicated that the healing effect of warm colours is greater than that of cold colours, and the healing effect of cold colours is greater than that of neutral colours. Combined with Table 4, it can be seen that the mean values of subjects' scores showed a trend of warm colour high brightness (WC-H) > cold colour high brightness (CC-H) > warm colour low brightness (WC-L) > cold colour low

brightness (CC-L), indicating that the healing effect of high brightness is greater than that of low brightness based on colour hue.

**Table 4.** Mean and standard deviation of brightness.


**Figure 5.** Box plot of emotion scores. Note: More asterisks "\*" imply a stronger correlation.

Warm classrooms have the highest mean value of 3.381 in the "pleasant/unpleasant" category while cold classrooms do not differ significantly from neutral classrooms. The difference between the mean scores of warm and cold colours after adjusting the brightness is large (almost 0.1–0.2 points), and the mean value of 3.518 in warm high-brightness classrooms even exceeds that of warm classrooms itself. It is clear that warm colours play a pleasurable role in the emotional state, and higher brightness colours also make the mood more pleasant.

In the "relaxed/unrelaxed" category, warm colours have a significant relaxation effect, with a mean value of 3.427. Meanwhile, cold colours have a mean value of almost 0.2 points higher than neutral colours, which is a substantial difference. In terms of brightness, although the difference was still significant, the difference between the mean value of high brightness for cold colours and low brightness for warm colours decreased, while the mean value of low brightness for cool colours dropped to a minimum of 2.754.

In the "focused/unfocused" category, although the highest mean value was still for warm colours, the score decreased compared to the previous two moods (3.327). The difference between the cold and neutral colour classrooms was again not significant. The mean score for warm high luminosity also declined in this item. Relatively speaking, cold high luminosity scored 3.255 and it is the highest score among the three moods. The same is true for cold colours with low luminance, indicating that cool colours are easier to focus on mentally.

#### *3.3. Different Effectiveness under Demographic Factors*

#### 3.3.1. Degree of Anxiety and Depression

Based on the results of the one-way ANOVA in Table 5, it can be seen that among the seven score dimensions, scores were significantly different across the anxiety population, as the significance tests were 0.02, 0.013, 0.016, 0.044, and 0.044. However, there was no significant difference in the cold-coloured low brightness classroom (*p* = 0.476 > 0.05). This corroborates the validity of H2 at the beginning of this paper.

**Table 5.** Results of the differences in the scores of each classroom on the three anxiety populations.


Note: Where 1 represents people with no anxiety symptoms, 2 represents people with "critical" anxiety symptoms, and 3 represents people with significant anxiety symptoms. Value in bold means significant.

From the results of the multiple comparisons, it can be seen that, for different groups, the scores of "people without anxiety symptoms" are higher than those of "people with severe anxiety symptoms" and the scores of "people with possible anxiety symptoms" were also higher than those of "people with significant anxiety symptoms". Therefore, it can be concluded that the emotional satisfaction of "people with significant anxiety symptoms" with different colour spaces is significantly lower than that of the other two categories of anxious people, which is probably due to their high anxiety values. In the cold high brightness classroom, the scores of those with possible anxiety symptoms were greater than those with significant anxiety symptoms. Based on this result, it can be seen that "people with 'borderline' anxiety" feel pleasanter with the cold high brightness colour space than "people with severe anxiety".

According to the results of the one-way ANOVA in Table 6, it can be seen that among the seven score dimensions, the three categories of colour classroom scores, neutral colour score, warm colour score and warm high brightness, also differed significantly across depressed populations with significance tests of 0.041, 0.001, and 0.013, respectively, all significantly smaller than 0.05.


**Table 6.** Results of the differences in the scores of each classroom on the three depressed populations.

Note: 1 represents people with no depressive symptoms, 2 represents people with "borderline" depressive symptoms, and 3 represents people with significant depressive symptoms. Value in bold means significant.

Based on the results of the multiple comparisons, it can be seen that for both the neutral and warm colour scores, the scores of "people without depression symptoms" and "people with 'borderline' depression symptoms scores were higher than the "people with significant depression symptoms" scores. It shows that "people with significant depression symptoms" are significantly less happy with neutral and warm colour spaces than the other two anxious groups, probably due to their high depression values. The "no depression symptoms" group scored higher than the "with significant depression symptoms" group for the high brightness classroom scores of warm colours. Based on this result, it can be seen that the "non-depressed" group felt pleasanter with the warm, high-light colour space than the "significantly anxious" group.

#### 3.3.2. Gender

According to the results of the independent samples *t*-test in Table 7, it can be seen that there is no significant difference in most of the different colour and brightness classroom scores by gender, but only in the warm colour high brightness classrooms. The significance test for the difference between the scores of warm colour high brightness classrooms by gender is 0.033, which is less than 0.05, indicating that there is a difference in the degree of preference for warm colour high brightness classrooms among students of different genders. Based on the mean values, it can be seen that females rated slightly higher than males, thus females have a higher preference for warm-coloured high-brightness classrooms than males. The remaining variables are not statistically significantly different in terms of gender because the significance is greater than the standard 0.05, so the original hypothesis cannot be rejected.



Note: Bold means significant.

#### 3.3.3. Education Background

We divided the education into undergraduate and master's degrees for comparison and the majors into science and non-science disciplines for analysis. According to the results of the one-way ANOVA in Tables 8 and 9, it can be seen that because the significance is greater than the standard 0.05 for all, there is no significant difference in each dimension score in both education and major, so the original hypothesis cannot be rejected. That means, there is no significant difference in judging the influence of teaching space on emotion among different academic majors, and the opening H4 is overturned.

**Table 8.** Results of the variance analysis of each dimension in terms of education.


**Table 9.** Results of the analysis of the differences between the dimensions in terms of profession.


**Table 9.** *Cont.*


According to the analysis of the results, the different demographic variables do not differ significantly in judging the influence of teaching space on emotions, overturning the opening H4.

#### **4. Discussion**

#### *4.1. Anxiety and Depression*

There has been some investigations about the effects of quarantine on psychology. One study [43] compared psychological outcomes during quarantine with later outcomes and found that during quarantine, 7% (126 of 1656) showed anxiety symptoms. A study [44] of hospital staff who might have come into contact with SARS found that immediately after the quarantine period (9 days) ended, having been quarantined was the factor most predictive of symptoms of acute stress disorder. Some scholars did a review [4] of the psychological impact of quarantine using three electronic databases. Most reviewed studies reported negative psychological effects including post-traumatic stress symptoms, confusion, and anger. And conclusion 1, indicating prominent anxiety and depression among college students during campus lockdown, is in accord with existing findings. However, one study [45] compared undergraduates who had been quarantined with those not quarantined immediately after the quarantine period and found no significant difference between the groups in terms of post-traumatic stress symptoms or general mental health problems. Although this is inconsistent with our conclusion 1, it provides a new perspective for our future research, which can compare the students' psychological state before and after lockdown.

#### *4.2. Colour and Mood*

Though no research has revealed a one-to-one relationship between mood and colour [46], it is believed that different colours have corresponding emotional preferences and different degrees of health effects [47]. For example, warm colours stimulate the spirits and help relieve depression, while cool colours are more calming and relaxing for nerv-ousness [48, 49]. Conclusion 2 agrees with the basic theories of colour psychology. In addition, in the view of colour psychology, colours with higher brightness are more popular than those with lower brightness. Conclusion 2 verifies this theory and is consistent with prior studies [50]. The study of Costa Marco et al. [50] on the colour of college students' dorm rooms indicated that blue interior spaces facilitate various learning activities and make it easier for students to be calm and concentrated. Chong Gao et al. [51] found that patients with depression symptoms find it harder to recover when in blue interior spaces, compared with white and warm interior spaces. Yildirim et al. [52] in their study of living room colours also showed that warm colours were highly stimulating to evoke mood, while cool colours were more associated with "expanding space" and "resting". Bilal et al. [53] suggest that neutral colours, such as grey, can reduce the feeling of pleasure for guests in hotel rooms. Thus conclusion 3 correlates with existing studies.

In addition, existing studies related to colour psychology have indicated that there are significant differences in colour preferences between genders. For example, Costa Marco et al. [50] discovered substantial disparities between men and women in their preference for blue and purple dormitory spaces. Al-Rasheed [54] concluded that gender-specific preferences for colour exist in both Arabic and English cultural circles, with men preferring blue green. However, conclusion 4 is not fully consistent with the existing studies. In addition to gender, other studies focused on demographic elements such as age and income, like Cho [55] who identified substantial disparities in household income and age in terms of satisfaction with the interior colours of luxury stores.

### *4.3. Limitation*

In addition, there are some limitations in this study.

This study is based on a relatively homogeneous geographical and cultural background, with subjects mostly coming from college students in Harbin, China, who are enrolled in universities with excellent academic reputations and good public images. In other regions, traits like language, lifestyle, weather, and ethnic background are all different. Comparison studies on different regions in China can be supplemented in the future. Additionally, this study mainly collected questionnaires during the school closure period. In future investigation, the range of subjects could be further expanded. A wide variety of students such as home commuting students, resident students, and even senior/junior students could also be considered.

This paper used the HAD scale to assess and classify the subjects' anxiety and depression symptoms. Future studies can increase the psychological assessment dimensions (e.g., the combination of multiple scales) to increase the credibility and accuracy of the evaluation. Apart from that, this study focused on the subjective feelings of the subjects, so the data obtained are subjective emotions. In the future, the physiological indicators of the subjects can be monitored and analysed in conjunction with real-life experiments. Moreover, only three emotional criteria, "pleasant/unpleasant", "relaxed/unrelaxed", and "focused/unfocused", were selected for evaluation, and there were few emotional indicators. Future studies can add emotional indicators to improve the evaluation.

In this study, for the sake of the controllability of the experiment and the accuracy of the results, other environmental components that affect indoor colour (e.g., light [56,57], furniture, material, etc.) were not discussed. Future studies may try to add relevant elements as variables to increase the exploration of more dimensions of colour in indoor teaching spaces. Furthermore, three hues and two kinds of lightness were selected for the study. The classification was simple and lacked specific colour values for support. In future, studies can take more colours and more colour dimensions (e.g., grey scale) into consideration, apply more detailed and specific classification methods, and combine colour parameters.

#### **5. Conclusions**

In this paper, a study was conducted on the emotional impact of environmental colour on college students in the indoor teaching space during the epidemic closure through a questionnaire survey method. The conclusions are as follows:


some differences in the experiences of people with different anxiety and depression symptoms in different colours of teaching spaces.

4. In most cases, there is no significant difference in the colour preference of teaching spaces between the gender groups. However, there is a significant difference between males and females in warm high-brightness teaching spaces, with females having a higher preference for warm high-brightness classrooms than males. There is no significant difference in colour preference of teaching space among the different education groups.

**Author Contributions:** Conceptualization, Y.W. and W.T.; methodology, Y.W. and W.T.; software, W.L.; validation, W.T. and W.L.; formal analysis, W.T.; investigation, W.T. and W.L.; resources, W.T. and W.L.; data curation, W.L.; writing—original draft preparation, W.T. and W.L.; writing—review and editing, W.T., Y.W. and W.L.; visualization, W.L.; supervision, Y.W. and F.L.; project administration, W.T.; funding acquisition, F.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was funded by [the Ministry of Science and Technology of China] grant number [G2021179030L].

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Appendix A**

**Table A1.** The Colour Evaluation Questionnaire of Teaching Spaces.


4–17. HAD Scale (Table 1)

Please observe photo group 1 carefully and answer questions 18–20 truthfully according to your feelings

#### **Table A1.** *Cont.*


26. This set of photos makes you feel ( ) very

Please observe photo group 4 carefully and answer questions 27–29 truthfully according to your feelings

29. This set of photos makes you feel ( ) very

unfocused unfocused general focused very

focused

focused

#### **Table A1.** *Cont.*

