Expected behaviour:

Savanna M and Savanna Plateau M should have darkish yellow brown grass. Birch Forest M and Hills M should have the birch forest grass color. Roofed Forest and Roofed Forest M have very very dark green grass color. Mesa Plateau biomes have mesa biome color for the grass foliage.

Actual behaviour:

All 6 biomes have the default grass color which is not right and doesn't match the regular biome. Mesa Plateau is generating desert grass foliage color instead of the mesa color.

Affected biomes:

Old Biome name	New Biome name	World seed & /tp coords	Java	Bedrock
Mesa Plateau (regular)	Badlands plateau	...	...	...
Roofed Forest	Dark Forest	Seed: 0, Coords: 2500, 75, 860
Roofed Forest M	Dark Forest Hills	...	...	...
Savanna M/Shattered Savanna	Windswept Savanna	Seed: 0, Coords: -1877, 105, -2315
Savanna Plateau M	Shattered Savanna Plateau	...	...	...
Birch Forest M/Tall Birch Forest	Old Growth Birch Forest	Seed: 0, Coords: 300, 64, -730
Birch Forest Hills M	Tall Birch Forest Hills	...	...	...

Steps to reproduce:

Just create a new world and check the M biomes I said, you'll see the grass color is different in the M biome form the regular one.

Seed 306959825, coordinates in the picture, biome map included. I haven't checked all M biomes.