Every pet is yellow with no way to tell quality for me.

This looks like a problem with the method I use for coloring rarity on battle pet frames. Try enabling the option to use Alternate rarity coloring.

Can confirm this happens to me as well every time an update is pushed. The "test old pet battle rarity coloring" setting gets reset and the colors look like this in a battle.

Oh, that option is resetting? Hmm. I can fix that. I wonder if it's worth reversing the default setting and using that method as the primary way of coloring names in pet battles.