My first boat had a painted hull.....Royal Blue...while new, it was gorgeous, but the paint was an
epoxy and after some years started to chalk.
So I repainted it with a lighter color blue, this time two part
polyurethane.
After several more years, I noted this lighter blue was prone to getting and showing dirt.
So once again, I repainted it, this time white, also two part
polyurethane. White didn't seem to show the dirt as much as the light blue.
I can't say I noticed much difference with the temperature inside the boat, as the hull was insulated. The hull, regardless of color, was hot to touch in the summer, mostly because it was a
steel hull.
My next boat (fiberglass hull) had a professionally applied two part white polyurethane paint job done to it, polished it looked like a million dollars. In the summer, the hull was hot to the touch.
Next boat after that, had a dark blue
gelcoat, as above, hull was hot to the touch, but inside was always relatively cool. Scratches and scuff marks were noticeable from the
anchor, dinghies alongside, fenders, etc.
Off the three, the dark blue hull...ala...Beneteau dark blue shows hull dings and scuffs more than the others. The
gelcoat is easily scratched and the white
fiberglass underneath becomes very noticeable. These dings and scuffs are difficult to repaint.
White, obviously will not show the above imperfections as much as other colors.
If not white, a lighter color might be a better option than dark blue.
Hope this helps.