red
黕 centers on a dark, sooty red color, like the deep red of dried blood or a smoldering ember. It is a rare kanji whose meaning is simply 'red' with a dark, muted quality.
黕 combines 黑 (black) with 冘, which likely contributes a phonetic element. The exact historical development is uncertain, but the character likely originally described a dark, sooty red color.
The left side is 黑 (black), and the right side 冘 looks like a person bending under a heavy load. Imagine a dark, sooty red color like the stain left by a blacksmith's soot mixed with a little blood from hard work.
For タン, imagine a dark red tan line on skin after a day in the sun: tan -> タン, and the dark red color matches the sooty red of 黕.