Most all buttons are mutts, if you consider mixed colors mutts. I don't know of anyone that has buttons that breed true to their color.
If you mean, all they are buttons, why yes they are! There just aren't any that would keep their own color. Now, if I put my cinnamon blueface pair together in a seperate cage, and my df silvers (if I still had the hen) together in the same cage, odds are that they would produce their color, especially the silvers. The cinnamon bf, I think, would produce some cinnamon, some cinnamon bf, and some bf, at least I think that's how it works.
Most everyone has 'mutt' buttons, there is only one breed, but many different colors!
If you mean, all they are buttons, why yes they are! There just aren't any that would keep their own color. Now, if I put my cinnamon blueface pair together in a seperate cage, and my df silvers (if I still had the hen) together in the same cage, odds are that they would produce their color, especially the silvers. The cinnamon bf, I think, would produce some cinnamon, some cinnamon bf, and some bf, at least I think that's how it works.

Most everyone has 'mutt' buttons, there is only one breed, but many different colors!