Still wouldn't really call them common if they're only sold by one, or two hatcheries.Please verify accuracy.. but fun read anyways..
https://cluckin.net/silkie-colours-2.html
Other related links..
https://vjppoultry.com/silkie-color-varieties/
Check out their learning center..
https://vjppoultry.com/best-of-articles-collection/
I've seen them available at Ideal.