Silk thread doesn't have color preserver and will darken by several shades. Will color preserver do the same thing as applying epoxy to the thread? Silk is strong and there seems to be lots of it on @#$%&. UV protection is important when coating the threads.

You are correct - there is no NCP silk, at least none that I've seen.

CP will initially darken silk just as it does nylon that is not NCP. However, as the CP dries the original silk hue will return.

Some epoxy formulations include UV protection as does spar, if that was you question.

CP on silk can be iffy as some CP works better that others, especially for the lighter pastel hues. Strongly suggest test wraps to determine what works best for you.

Like Don recommended, do some test wraps with and without CP. Use a scrap piece of blank that is the same color as the blank you want to build on. If you don't have a scrap piece, just put the test wraps where your grip is going, test wraps can be removed easily.

I would recommend the Al's Silk Color Preserver, Anglers Workshop sells it, that stuff has worked very well for me over Silk.

I've used Al's for many years, works on nylon also. The difference for me is Al's seems to be less likely to leave shadows, or blothes on silk.