白髪
しらが · shiraga · JLPT N2 · noun
hair
白 (white) + 髪 (hair) = white hair, read しらが
The reading しらが is irregular: 髪 is not read かみ here. Modern slang uses the same word for trendy hair bleaching.
白 — pictograph; resembles 日 (sun) with a stroke on top
白 is generally considered a pictograph, traditionally explained as depicting the sun rising with a ray of light above it, hence the meaning 'white' or 'bright.' Some scholars instead see it as a drawing of a thumbnail or an acorn. From 'bright' it extended to 'clear,' 'plain,' and 'to state plainly.'