I make outdoor statues of epoxy resin and fiberglass and am having a lot of trouble with the epoxy turning yellow out in the sunlight after some months. I load the epoxy with titanium dioxide pigment to make it white but it doesn't stay white. Is there some really white paint that will stick to epoxy? Is there some secret that I should know? Any help would be appreciated.

You need to paint it. The epoxy degrades in UV (like sunlight)
whether or not there is pigment in it; you need paint (or something)
_on_it.

If you don't like the look of painted epoxy, varnish will stick fairly
well, if you sant the surface to about 600 grit first. There are some
spray epoxy appliance paints I've had good luck with; go to the
hardware store and tell them you're painting a fridge. You need to
scrub the epoxy with a green plastic brillo pad before painting, to
remove the blush ( a kind of waxy coat that forms when the epoxy
dries).