Personally I like black. It looks good, doesn't show the dirt, and puts the
focus on the boat.

Only think I don't like is it doesn't stand out. I have lights & running
lights on the side, but
this past weekend I needed to park it for a while at night on a street in
the Boston area.
I was somewhat worried that people would not see it because It's black and
is not as
tall as a car. (The boat was not on it). But that is a very unusual
situation.