How to make an entity with multiple textures? [1.16.5]

So I've been trying to make an mob that can have multiple textures, and the mob has the Witch model, and I can put a texture on it but I don't know how to make it spawn with a random texture.

I tried searching through mobs that have multiple textures like the fox, rabbit, and stuff but I wasn't able to find out how to do it and I kept getting errors when i tried compiling:

error: method createKey in class net.minecraft.network.datasync.EntityDataManager cannot be applied to given types; private static final DataParameter<Integer> ALCHEMIST_TYPE = EntityDataManager.createKey(AlchemistEntity.class, DataSerializers.VARINT);
^
required: java.lang.Class<? extends net.minecraft.entity.Entity>,net.minecraft.network.datasync.IDataSerializer<T>
found: java.lang.Class<net.newblocks.entity.AlchemistEntity>,net.minecraft.network.datasync.IDataSerializer<java.lang.Integer>
reason: cannot infer type-variable(s) T
(argument mismatch; java.lang.Class<net.newblocks.entity.AlchemistEntity> cannot be converted to java.lang.Class<? extends net.minecraft.entity.Entity>)
1 error

And sorry there isn't much info, this was the only error that appears when I tried to copy the same thing from one of those mobs with multiple textures (plus imports). I already tried searching on the site and didn't find much. I can provide more info if needed