This is the new mango marking pack for FeralHeart.
The thing I react on the most here is that it doesn't really show as it would normally if there was a problem. If it was a material problem and it was looking for something that doesn't exist it would be white. If it was a texture problem and the game was looking for a texture that didn't exist it would be yellow and black.
This makes me think it could be a rendering issue, especially if you look on that weird artifact looking part on the bottom of the tail. Try changing your rendering mode in video options, restart the game and see if it does anything. If it doesn't help, do you have anything installed such as GUI mods or textures using those colors?
They're not exactly normal to show in the game.