A stock gelcoat match on a 25 year old boat will be difficult to find and likely not match perfectly even if you do find one. The easiest way to get a perfect match is to send a sample/plug to a gelcoat shop and they can match the color exactly. The one I use up here in Seattle, but they ship worldwide is GCP (Gel Coat Products). They do a great job of matching. You can also give it a shot yourself, but its more of an art and I have found I'm not gifted in that way. Also, topside gelcoat and deck/cabin house gelcoat are often not identical - Usually different batches since they were made likely in different areas of the shop.