I would say buff because there are very few. I think I read somewhere there is someone in FL working on a line of show quality buffs. I've never seen one myself. After that, I would say opals. Around here (GA), there are a lot of breeders that have very nice-good type and color birds. Competition at shows is fierce. OEGBs always have the largest number of entries. If you have a bird of very good type, it really doesn't matter which variety it is, it will sell. If you have a perfectly colored bird of poor type, it won't (except to someone who doesn't know any better). I saw a pair of white OEGBs for sale at the Nationals that I would have given my right arm for (and I have never particularly wanted the white variety). The rooster was as close to perfect type that I have ever seen. People were crowded around the cage looking at them. Unfortunately, my right arm isn't worth $1500 which is what they sold for. My point is, breed for superior type with color being secondary and you'll always have people wanting to buy your birds. Also, listen to the old guys that have been breeding OEGBs for decades. I've learned more from some of those guys in 5 minutes than any book. PM me if you want some names and numbers of breeders in GA, AL, TN, NC. Lots of good ones in the Southeast.