sun tach wiring q's

gotta old tach today outta a scrapped piece of machinery. it's a sun super tach. has 4 wires red I assume is power black assumed to be ground green I am sure goes to the dizzy negative and blue? what's blue?

Lights maybe...

Blue is for the tachometer light, wire to your cluster/dimmer.

I have a SunPro tach in my B2200, has worked fine (guess 10 years).

ok thanks