Most pigments are compatible with epoxy, even those made for use in fiberglass. Though polyester based, they act in epoxy as nonreactive diluents. The problem is opacity. The typical pigment is loaded at between 2% and 4% so as not to compromise the physical properties of the epoxy. At that loading, the mix is nowhere near opaque. That would be the problem Val referred to.

I had the same problem once on 35,000 sq. ft. of Air Force hangar floor once; at maximum permissible pigment loading, the color was barely perceptible in a clear epoxy primer. Even a topcoat of aliphatic polyurethane didn't cure the opacity problem.

Just thinking out loud here, maybe a solution would be to paint the seal coat out of high quality epoxy paint, and glass over that? Maybe use the same paint for fill coats? Maybe lay up a test panel of glass wet out with the same paint? There are any number of high quality marine epoxy hull paints that could be used for this, but the application as a wetout resin has some big question marks.