经、史、子、集四部颜色依春、夏、秋、冬四季而定，分别是绿色、红色、白色（或浅蓝色）、灰黑色。

Following the symbol colors of four seasons, Spring, Summer, Autumn and Winter, book covers of the Four Divisions were respectively printed green, red, white (or light blue) and dark grey.

youdao

经、史、子、集四部颜色依春、夏、秋、冬四季而定，分别是绿色、红色、白色（或浅蓝色）、灰黑色。

The colors of classics, history, philosophy and belles-lettres were selected according to spring, summer, autumn and winter seasons, which were green, red, white or light blue and grayish black.

youdao

以二乙胺和二硫化碳为原料，经双氧水（27.5%）氧化，一步合成了四乙基秋兰姆化二硫。

Tetraethyl thiuram disulfide was synthesized one step from diethylamine and carbon bisulfide with hydrogen peroxide (27.5%) as oxidant.

youdao