noun
Refers to the painting itself or the art genre. Common in art contexts.
彼女は美しい水彩画を描いた。
She painted a beautiful watercolor.
水彩画の展覧会に行ってきました。
I went to a watercolor painting exhibition.
日本画 refers to traditional Japanese-style painting, often using mineral pigments, distinct from Western-style watercolor.
Compound of 水彩 (watercolor) and 画 (picture, painting). 水彩 is itself from 水 (water) and 彩 (coloring).