Skylight filters have a very pale pink tint which is supposed to correct the slight blue cast you get when shooting under an open sky.
In practice, the effect is so subtle that it's hardly noticeable. I left skylight filters permanently fitted to all my lenses as lens-protectors when I used to shoot on film.
Shooting on digital has rendered any sort of coloured filter largely redundant. Given the choice, I'd use an untinted UV filter as a lens protector.
A.