Looks like a '67 CL90 - Front brake switches were not standard at that time, I don't think.
Previous post suggested it might be a newer cable wired for a front brake swtich, and that's probably correct.
If you want a front brake light, just run those wires to the same-colored wires anywhere on the bike.
Black is hot (after the key switch), green/yellow just provides a path to ground so that one can just go to a green ground wire anywhere (green is always ground on these bikes).
bill