noun, noun or participle which takes 'suru'
coloring; colouring (a drawing)
Refers to the act of adding color to a drawing, painting, or illustration. Often used in art contexts.
彩色 is a more general term for coloring or painting, while 着彩 specifically emphasizes applying color to a drawing or line art.
Compound of 着 (chaku, 'to attach, apply') and 彩 (sai, 'coloring, hue'). The exact historical derivation is uncertain, but the kanji combination naturally conveys the meaning of applying color.