My Little Pony: Friendship is Magic - Steampunk Celestia Must Be An Alchemist.

It's funny that Luna and Celestia don't have a "define" skin tone/most seen skintone compare to the other girls.
Either Celestia is light skin to represent the light of the sun or tan to represent its effects on the skin. Either Luna is pale like moonlight or dark skin as the night. It's rare to see them both dark skin..

Dark skinned Celestia? … Actually that makes a lot of sense.