noun
dried rectangular cakes of water paint (for Japanese-style painting)
Refers to solid watercolor pans used in 日本画 (Nihonga) and similar traditional painting. The term is specific to this format of paint.
See also: 日本画
日本画を描くときは、顔彩を水で溶かして使います。
When painting Nihonga, you dissolve the dried paint cakes in water to use them.
この顔彩セットには、よく使う色がそろっている。
This set of paint cakes includes the most commonly used colors.
The term combines 顔 (face, surface) and 彩 (coloring), likely referring to the colored surface of the paint cake. The alternate spelling 岩彩 uses 岩 (rock), possibly alluding to mineral pigments, but the exact derivation is uncertain.