There are recessive genes (blue eggs for example,called celadon) that you need two copies to get expressed. Then there are sex-linked recessive genes (like roux that makes a reddish bird) wherein females have only one copy so will express it but males will need two. Then you have genes that are codominant so are expressed more strongly with two copies. Then you have genes that are considered base colors (wild, fawn, EB) that all birds carry while other genes are modifiers that change the way the base is expressed (silver, blue, roux, fee…). Then there are other patterns/colors that could be a base pattern in themselves (pansy, ginger, black?) rather than modifying the ‘traditional’ base colors. Quail color genetics are multi genetic, many genes interact between colors/patterns, and new ones are always cropping up. Are you asking which is the rarest so you can breed it? Instead I’d find a color you enjoy or maybe one with multiple genes and try breeding for it. I also wouldn’t recommend intentionally heavily inbreeding for a particular color rather get a few birds who carry it and start with a wider genetic pool.