Lacking color

WAN

Think of how someone might look after a long illness or sleepless night.

"Lacking color" points to wan, a word that describes something pale or sickly in appearance. It’s a straightforward definition—no wordplay here—since wan literally means having little to no color, like a tired face or a dull sky. The clue avoids tricks, relying on the direct meaning of the word to guide solvers.