I see absolutely nothing in the appropriate UL standards to preclude painting any ladder.
The instructions DO caution that certain solvents, etc, may damage the ladder.
Yirtually all fiberglass tools, including ladders, have an outer layer of pvc, or other plastic, to "seal in" the ends of fiberglass strands- so any outer surface coating is unlikely to even reach the load-bearing parts of the material.
More to the point, painting of ladders and other equipment is a common method of identifying them. I am sure that we can all agree that making things harder for theives is a good thing. In that respect, "ugly" is beautiful.
