Sabino and Dominant White are still open for the time being, but if the trend of maximum sabino horses being created, that will likely be the next color type to close.
I am trying to keep the registry as realistic as possible and the numbers of patterned TB's, while growing world wide, are still extremely limited in numbers when considering the overall breed numbers. Since the registry doesn't even have 300 horses the numbers of rare patterned foundations are also going to be low.
There are several TB breeders in the community that specialize in rare colors and patterns and all of them are more than willing to work with other farms to set up a breeding or do a foal request. I encourage TB owners to look into this option before they create and register another patterned foundation.