Track Point Color in 3D Camera Tracker

Hard to find any info on these colours. I think those are an indication of the quality of the point: the greener the more accurate. But I don't know the priority order of all the different greens.

I don't believe they mean anything. The most important thing to do with the Camera Tracker is to set an origin and ground plane then insert a solid and add a camera on on the ground plane and then check the tracking. If the solid does not track properly and the perspective does not match then you did not pick a good origin and ground plane or the track is no good. The former is the likely problem. Once you have a good solid origin and ground plane it is pretty easy to attach solids or nulls to planes in the shot but you have to realize that the planes that you pick for your targets must match an actual plane in the shot if the object is going to stick. Otherwise, it will float like any object in the real world will float as perspective an parallax changes while the camera moves.  Adding a Grid to the solid placed on the origin and ground plane will help you figure out if you have a good track.