It means that the whites were the original color developed for show, so they have better body type, but I believe recently black silkies have also been showing very well, thus the added color.
As for what colors they come in, you can google the APA's breed standard for silkies, but the acceptable colors are black, white, blue, buff, gray, partridge and recently lavender.
However, there are a lot of unrecognized colors they come in as well, but I don't think they breed true as far as I understand it.
On a completely unrelated note, my splash silkie chick is a hot mess. It's feet were dry and extra scaly, and looked a little bloody/crusty so I coated them in vegetable oil. It's eye looked more swollen than it had before so I made an elizabethan collar out of cardboard, gauze and coated it in electrical tape because I caught it scratching it's eye. Gonna keep putting the teramycin on it but it tries to wipe it off.
I honestly don't know what's wrong with it. If I mess with it's head a lot (to apply medicine or put the collar on) it sneezes, but there's no discharge so I assume it's mostly from me poking it in the nostrils. I separated it from it's sibling finally as the other bird is showing no signs of illness.
I've begun putting Sav-a-chick in it's water and gave it some egg and some yogurt today along with it's chick feed, is there anything else I can do for it? I don't want to needlessly administer antibiotics.
If I knew for sure what was wrong with it was something chronic/respiratory, I'd give it back to the woman I got it from, but I keep hoping this is just mites and conjunctivitis made worse by the scratching.
I removed the post due to it was completely unrelated to your question.
