Nothing wrong with black gelcoat either. Just give it a polish and throw some stickers on it:
The lighter gelcoat colours are easier to work on and I guess white is popular as it would be the cheapest and most abundant colour.
The colour of the gelcoat doesn't affect paint. Even most stone chips only go back to primer.
If you already know your final colour, certainly wouldn't hurt to get gelcoat to match as close as possible. Will help you match fittings/finishes to body colour as you can try them against the gelcoat colour and could help with stone chips.