I don't like this because many of these transition colors I don't really consider blue or green but some sort of blue-green or green-blue.

I would also trust the results more if it bounced you around a bit randomly rather than tried to center you in. It gets to a point where I don't really have confidence and I suspect the environment around me contributed a fair amount at that point.

Seem to get ~172.

I feel the same way, after the first couple of responses, I was just thinking it's blue-green. So I just had to pick randomly.

A better interface would have been to just show the final spectrum pic and slide to where you think the separation is.