I used some rustoleum oil based paint in my bilge area, and it has held up very well so far. I just got a quart from home depot and prepped it real good applied two coats and have been very happy with it so far. used a semi gloss so any water would run off better and did it when the temp was up in the summer. I think it was only about $10.00-$12.00 and can be mixed any color you want.
For a black color, I recently tried out some graphite powder in epoxy and it worked very well. Shiny, very tough, and according to other users won't fade or degrade in sunlight due to the graphite.
This is under my cooler thats built in the floor.I have to remove 4 screws to get to it.
I was running new bilge pump wires and put in another 1100GPH pump.Just wanted it to look nice..No one will see it but i know its there...