I typically build ships with gray hull, although I'll highlight components with sensible colors (black gun barrels, hazard stripes around moving objects, etc.) A big part of my reasoning for this is that it reduces the resource cost for building the ship. It's a habit I got into partly due to the amount of gray hull salvaged from stations in early builds, and even more so when blue asteroids were so hard to find. When I first started playing the game I liked brown (perhaps from my Amarr days in Eve?) Since most of my ships are combat vessels, I have a hard time getting beyond "battleship gray." I'm getting better about going back over a ship after it's built to give it a color pass and break up the monotony. My salvage ships are typically bulldozer yellow/black, or John Deere green. Civilian ships I've built are much more colorful, though I tend to veer towards blue or red with white.
I like black, but it's a pain to build with because you can't see what you're doing. It always reminds me of Disaster Area's black ship from Restaurant at the End of the Universe. "It's the wild colour scheme that freaks me,'' said Zaphod whose love affair with this ship had lasted almost three minutes into the flight, "Every time you try to operate on of these weird black controls that are labelled in black on a black background, a little black light lights up black to let you know you've done it. What is this? Some kind of galactic hyperhearse?''