That means it’s working just fine. All of the horse skin recipes are either black or white. There are multiple black and multiple white recipes, because the “unskinned” horses come in different variants: buckskin tan, dapple grey, brown/white pinto, and bay brown.
That’s why there are 4 black horse recipes and 4 white horse recipes:
- buckskin tan horse + tainted fodder -> black horse
- buckskin tan horse + tainted fodder -> white horse
- dapple grey horse + tainted fodder -> black horse
- dapple grey horse + tainted fodder -> white horse
- brown/white pinto horse + tainted fodder -> black horse
- brown/white pinto horse + tainted fodder -> white horse
- bay brown horse + tainted fodder -> black horse
- bay brown horse + tainted fodder -> white horse
So, for example, if you have a dapple grey horse and a tainted fodder in your inventory, you should have 1 white horse recipe and 1 black horse recipe enabled, and the other 6 will be greyed out.
If that’s the case, then there’s no bug and everything’s working fine.