Bottom black radical (Kangxi #203) - a soot-smudged face above a fire underneath, the 12-stroke pictograph of black grime. Carries the meaning directly:
黛 is a dark blue-black pigment used by ancient Chinese women to paint their eyebrows. Same radical in
默 (silent, lit. 'dog of darkness'),
黯 (dim),
点 (dot, originally a black mark).
