Andy, just looked at a wiring diagram. there are 3 wires on this drawing, 1 green, 1 green + yellow stripe, 1 black. the green is the negative, the others are the tail +brake. the green will go to the metal frame of the bulb via the bulb holder. the others go to bulb filaments. you can swap these two wires over with no problems but the wrong light will come on. SWAP THESE 2 ONLY if tail + brake are mixed up.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix motorcycles.