The skin of ripe apples is generally red, yellow, green, pink, or russetted although many bi- or tri-colored cultivars may be found.
Apple skin may also be wholly or partly russeted i.e. rough and brown.
The skin is covered in a protective layer of epicuticular wax.
The exocarp (flesh) is generally pale yellowish-white, though pink or yellow exocarps also occur. (source)
So can rabbits eat apple skin?
Yes apple skin is fine for rabbits to eat.
Just don’t give them too much as it is quite acidic in its nature for bunnies.
However, they will enjoy it if they are given it to eat.