green is antifreeze. Maybe it froze, and cracked something (worst case scenario) or just got slushy and pushed a bit out when expanding somewhere ... I had this happen to me when I lived in N.O. as I thought the mix was sufficient but it was just a bit too much water and it was frozen in the radiator but not enough to push out a plug or crack the block or heads. Learned of the issue when it overheated and cracked the head (sluh pluged the radiator so now water flow), but possibly it is something else. Hard to diagnose from afar.
Check the radiator at the cap, and at the reservoir, then if both are full likely no leak and it forced a bit out. if low, try to check the antifreeze (refractive index or specific gravity checker) to see what the protection level is and if it possibly froze. Otherwise top it off, and see if it finds its way back out. pressure check if possible as well. otherwise I'd start the bike and warm it up while keeping close eye on the temp.