I don't know if there's a qualitative difference between color for a concrete/fiberglass vs. a shot-crete/plaster pool. My pool builder talked me into white plaster, but I had and have some mild regret over the finished appearance. An aesthetic choice, perhaps; I wanted an island lagoon, the contractor preferred conventional bleached-white California. There may be a heat retention benefit to a darker surface, but I've heard that some customers are less pleased with the uneven color or blotchiness that may present over time. Is this also true for painted fiberglass? I leave this question to be answered by those experienced with fiberglass surfaces.