26 x 1-1/2 (French 650B, ERTO 584)) was a fairly rare size in the US for some time. These are getting easier to find and there is a better selection now that 650B mountain bikes are becoming trendy.
If you're looking for 26 x 1.5" than disregard the above statement. Those were popular on entry level mountain and city bikes. Just about any decimal sized (1.5, 1.6, 1.75, 2.0 etc...) mountain bike tire will fit those rims.
You'll probably be stuck with black or black with gumwall for either size.