dappled
驒 centers on a dappled pattern, specifically describing a horse with a mottled or spotted coat.
驒 combines 馬 (horse) with 單, which likely contributes the sound and may relate to the idea of a single or distinct pattern, referring to a dappled horse.
A horse (馬) with a single (單) distinctive coat pattern: dappled spots across its body.
For タン, picture a tan-colored dappled horse: tan -> タン, and the horse's coat is covered in tan spots.