black
黔 centers on the color black, often with a sense of darkness or sootiness. It is a rare kanji used mainly in historical or literary contexts for blackness.
黔 combines 黑 (black) with 今, which likely contributes a phonetic element. The exact historical development is uncertain, but the character is associated with blackness or darkening.
The left side 黑 means black, and the right side 今 looks like a person under a roof. Imagine someone covered in soot under a dark roof, turning completely black.
For ケン, picture a black ink stain on a white canvas: the stain is a dark 'ken' (as in Ken, a name) that spreads. Ken -> ケン, and the blackness covers everything.