[Al Skierkiewicz]

If you haven't done so check out the picture Steve links to above. In addition to starting out very neat, all of the power devices are fairly close together. This keep wire runs short (more power to the motors) and has less weight than spreading them all over. (Steve, I may like to use your photo as demo example. Would that be OK?)
Venkatesh, I think you mean #10, that is the minimum wire size for most of the motors and power to speed controllers. #10 Zip cord, colored red and black, is available in spools from Newark. It is fairly flexible, easily routed through mechanical stuff and quick to terminate. Follow Venkatesh's advice for soldering all crimped connectors. I know it sounds like suspenders and a belt but you can't play if you don't work.
Color coding is easy with 3m EIA colored tape, available from Digikey. This comes in rolls of ten colors, I think 3-5 yards of each. We wrap each wire from power distro to speed controller, from speed controller to motor, PWM cable, circuit breaker and CB location. position on RC and spike or victor. With one glance you can see which PWM cable on which RC output feeds which speed control or spike which in turn feeds which motor and know which circuit breaker to pull to disable the circuit or which one to put back when you have removed them for troubleshooting.