It depends on when it was made.
Coach changed, added and deleted colors on a regular basis, and several new colors would be added every year. If a color was available on the classic styles during Year X and Season Y, it was probably available on the Prairie Bag.
Find a color you like and have it authenticated, unless someone has the spare time and is willing to look through years and years of files and catalogs and individual season"s worth of available colors. What's available is what's available. You can't call up the Used Handbag Factory and order one in the color you want, so be patient and wait to find a color you like and in the condition you want, and that's confirmed as authentic. Narrow your search down to a specific color and take your time looking for it. Good collections require time and patience, and above all, restraint.