I'm afraid I don't know much more than what is on the Wiki Spoon.
It wasn't until after the Micro ToolClip was discontinued that I was even aware they made it in colors other than black.
As regards rarity, there seems to be five or ten black ones for every colored one, with green perhaps turning up less frequently than the others. Not a very scientific measurement, I know.
On a related note, here is a couple scans of a SOG brochure from the mid-1990's. Notice that they show all four colors:
Ironically (or not) these appear to be the same four colors that the Auto Clip knife was produced in, shown elsewhere in the same brochure: