I've said it before, and I'll say it again . . .
Painting is one of the worst things you can do to a Hobie Cat. Gel coat can be sanded and refinished several times. Paint will chip and wear through quickly, exposing the underlying color. It's really hard to get a paint finish to look good. It fills the pattern on the non-skid. It adds weight. It makes the boat harder to repair.
Andy Larson has the black 17 - but it was re-gel coated, not painted. It looks cool from a distance, but not so much up close. Black shows off every imperfection in the surface - and it gets noticeably dirty much faster than a white boat. I don't know about the heat factor. Andy's on the forum, so maybe he can chime in.
It's your boat, so you can do what you want with it, but I hate to see a nice "barn boat" painted just because you don't like the color.