As mines in bits Im not 100%. As long as its earthed. I had mine earthed here, which is where horn goes. But looking at Haynes manual theres no blue wire. I would have to muck about with a meter to find out what it is for exactly.
no problem found picky on google ages ago when I had earthing issue on mine although my bike does not seem to have that wire think the ie model is different to carby doh