Making Ore Mob Texture change based on y

Alright so here's the prompt: I want to make my custom mob "Ore Dwellers" texture change based on its y level whats the best way to do this?
Like if its above 30 (not a negative but a positive) then do coal, iron or copper textures, and lower different textures. What's the lag free-est way to do this? I'm working in 1.21.10.