What do the colors mean?

[steveo]

ok because the xlc is thicker than the standard xl cause of the fins is a 66t spur and a 18t pinion going to mesh, i have a 72t spur and i think a 18 or 16t pinion on now, and i have maybe have an 1/8 to play with before the motor is touching the tranny, its a 7xl on 12 cells and every one says to start with a 66t spur and 18t pinion, so before i buy i would like to here your opinions for any optional gearing, i hate buying stuff i cant use

thanks fellas