灰
huī · HSK 7
ash
灰 = hand (又) over fire (火): ash is fire gone cool enough to touch
The top stroke comes from 又, a hand, set over 火, fire. Ash is what's left when a fire has died down enough that a hand can reach in. The huī sound also rides along in 恢 and 辉.
灰 — hand 又 (ナ) + fire 火
灰 originally depicted a hand (ナ, simplified from 又) holding or reaching into fire 火, representing the cooled ashes one can safely pick up after a flame dies. From this concrete sense of 'ashes,' the meaning extended to the color gray and figuratively to discouragement, as in 灰心.