get red
赧 centers on the visible reddening of the face, typically from embarrassment or shame. The core idea is a sudden flush of red.
赧 combines 赤 (red) with a phonetic element that likely contributed the sound. The character expresses the reddening of the face, especially from shame or embarrassment.
The left side 赤 means red. Picture someone's face turning red as they blush deeply: 赧 is that sudden flush of red.
For タン, imagine a tan spreading across someone's cheeks as they blush: tan -> タン, and the red color rises.