*2.1. Sample Preparation*

The purple leaf Chinese cabbage samples from different breeding backgrounds with distinct color phenotypes were collected from Beijing Vegetable Research Center (Beijing, China, 116◦30 E, 39◦94 N). Specifically, the purple color trait was from the variety of 15NG28, as previously described [21], and the green parents were different Chinese cabbages with distinct shapes of leaves, holding patterns, and maturity traits. Totally 106 PCC samples were harvested and transferred to the laboratory within half an hour on 19 November 2021. Then, the vegetable leaves of each sample were cut into 2.0 cm length pieces, uniformly mixed, and freeze-dried (BIOCOOL vacuum freeze dryer, Boyikang Co., Ltd., Beijing, China). The dry samples were ground into a fine powder, passed through an 80-mesh sieve, then stored at −40 ◦C for further anthocyanidins content determination and NIR spectral profiles acquisition.
