I feel tormented by this statement. Just to share with you my experience with B+W Kaesemann filter. Recently has developed this concentric ring of (rainbow) colours around the rim. Initially it was just some faint watermark, it is so bad that it affects the photos.
I brought it back to Cathay Photo, initially they refused to help saying they have not been bringing in this product for a while now. After much persuasion, they reluctantly send a note on my behalf to B+W in Germany. I have yet to read the reply, but in short, they gave some reason why the filter can be screwed and that they cannot do anything about it.
I thought I had invested in a quality piece of polarizer, but I guess I am terribly wrong.
Skylight is a (very) little pinkish, and UV(0) is colourless and supposed to reduce a little haze. Personally, it does not matter to me whether it is a UV or skylight on the lens.
By all means, use a high-quality multi-coated filter from Hoya or B+W, and you will be keeping your lens safe without much compromise in optics. Or if your prefers used the original Nikon L37c.