Custom colors on 1.21

[Jishuna]

Overview

Commit b6eeaab for 1,20.1 added options for customizing grass and foliage colors, however this commit has not been ported to any 1.21.x versions. The included changes look to be self-contained and should be able to be directly ported.

Why would this feature be useful?

Adding feature parity to 1.21.x versions.