They bloom....the bloom is the protective coating on the eggshells. Sometimes the coating is thicker which gives it a whiter tint. This makes a terra cotta egg look a little pink.
Yeah, if you get it wet it should turn brown. When it dries it might look purple again. There is a coating on it, whether it be extra calcium or loads of bloom.
My RSL Queenie used to lay lots of eggs like that.