Found some green coolant around the base of the pre-cat O2 sensor when I was under the vehicle looking for leaks of coolant (chasing a slow persistent loss of coolant from the recovery bottle, already found some coming from underneath radiator). Oil and coolant appear clean.
But surely green (so not mixed with something) coolant cant leak around from where the O2 sensor is going into the (pre-cat)exhaust part??
Might be dripping from somewhere above..unto the O2 sensor.

 

Yes, most definitely leaking from elsewhere.