Ah, the good old grass top texture issue. Grayscale grass texture on top of a dropped aether grass block item. See attached:

(To be added to https://github.com/devs-immortal/The-Aether/milestone/1 )

Re-test is warranted here, unable to reproduce this in the latest version of 1.16.5 nor 1.17

Assuming resolved in 1.17

The grass top texture is also gray when held in the player's hand. Seems to smoothly change from gray to colored based on the player's pitch rotation.