3) Not getting hot in the sun

Actually, anything else than white will get warmed by the sun. I owned a full carbon A cat with no paint on and you could cook eggs on. Every foam looses stiffness at a certain temperature which is easy to reach with colored hulls. When I went to sunny Italy for the Worlds at that time, I painted the carbon A white in fear otherwise the boat wouldn't survive. Later the boat became light green, and even in the cold Netherlands, it became so hot you couldn't touch it.

A few years ago, light grey hulls became fashion in the A-class. It is a very very light grey. Even those boats can become very hot in the sun while a white boat parked next to them nearly doesn't heat up. When looking at the grey, its so close to white, but still it heats up quite easily.

Nowadays epoxy prepeg vacuum build sandwichconstructions mostly uses a stiffer foam with a higher temperature resistance and can deal with heat by sun more easily.
I think Marstroem cats are a good example of this. The autoklave baked VX40 even were completly pure carbon look black.

If you choose a color, you can easily test it by making a sample and lay it in the sun to see how much it will heat up.

Good luck!