[EricH]

Sorry, Chris. Blue is a legal color for ground per 2010's <R48-B>, as is black. Green is not legal on PDB branch circuits (red, white, brown, or black with stripe is legal on + connections, <R48-A>). (NOTE: May change for 2011, does not apply to non-PDB circuits like sensor returns)

Green implying earth ground is not relevant for FRC robots, as they don't have an earth ground unless it's specifically installed, and then it's typically a drag wire attached to the frame.

Given the question, I'd guess that green is a team color code for something else--and green is currently on the robot.