To the best of my limited knowledge, only one set of the "rainbow" SAA's were ever made. As I recall, they were aimed (no pun intended) at the SAA hunting crowd. I think USFA was going for a "camouflage" effect with these guns.
A few years back I saw them listed on GunBroker, being sold as a set. Not many bidders, if any, as I recall. I wonder where they are now?
Major 2: I, too, liked the looks of the short barreled Omni-Potents. Tried, in vain, to get one with a 4" barrel. Longer barrels on the Omni had a tendency to feel very muzzle heavy and, from what I understand, were not all that comfortable to shoot.
Coffinmaker: I, for one, attribute the demise of USFA to the ill-conceived .410 SAA. It was the last, futile attempt on USFA's part to bring something new to the market. Unfortunately it seemed to ring their death knell. Lack of a closing loading gate made it a pretty much useless firearm and with several other manufacturers (S&W, Taurus, etc.) already making D/A .410's it was the answer to the proverbial question that no one had asked.