(Because cows were added in Minecraft Alpha 1.0.8 before texture packs existed, this first appeared in Minecraft 1.2.2 Alpha for cows, Minecraft Beta 1.9 Prerelease 1 for red mooshrooms, and Minecraft 19w08a for brown mooshrooms)
The right/left horns, and all four legs of the cow, red mooshroom cow, and brown mooshroom cow cannot be independently retextured from one another, making them always look the same, limiting the player's resource pack creativity.

Steps to Reproduce:

1. Download and apply the following resource pack:
   CowVariants.zip
2. Spawn one of the following:
   1. Cow
   2. Red mooshroom
   3. Brown mooshroom

Observed Behavior:

Both the horns, and all four the legs of the mooshroom will look entirely red, despite the player seemingly only modifying one horn and one leg in the UV map.

Expected Result:

Only one of the mooshroom's horns and legs would be altered, since that is what the player intended to change. The current behavior is unexpected and not resource pack friendly.

Screenshots/Videos:

Notes:

1. Related independent retexture issues:
   MC-271355 MC-271384 MC-271383 MC-271368 MC-271363 MC-271357 MC-271355 MC-271354 MC-271330 MC-271305 MC-271304 MC-271232 MC-264571 MC-270516 MC-270517 MC-145334 MC-265343 MC-265345 MC-270530 MC-271767 MC-271768 MC-271769 MC-271770 MC-271773
2. Related mooshroom texture issues:
   MC-271515