2.5.4. Color

The PHBV films color was determined using a chroma meter CR-400 (Konica Minolta, Tokyo, Japan). The color difference ( Δ*E*\*) was calculated using the following Equation (3) [1], as defined by the Commission Internationale de l'Eclairage (CIE):

$$
\Delta E^\* = \left[ (\Delta L^\*)^2 + (\Delta a^\*)^2 + (\Delta b^\*)^2 \right]^{0.5} \tag{3}
$$

where Δ*E*\*, Δ*L*\*, Δ*a*\*, and Δ*b*\* correspond to the differences between the color parameters of the sample films and the values of the control film (*a*\* = 0.87, *b*\* = –0.38, *L*\* = 89.82).
