In speaking of breeds of livestock, all registries have "breed standards". All breeds have occasional genetic throwbacks that don't fit the standard such as: Red color in Holstein & Angus cattle. These used to be culled, now they have the red Holstein and Red Angus as registered cattle. In the Quarter Horse Registry in past years excess white markings or entire white or cream colors were unacceptable, now they have changed color rules so that you have either a Quarter Horse or a Paint Horse.Also many dog breeds have color requirements. The white color was selected by the Original Researchers at Utah State University when selecting  for the St Croix breed. This was to make them as consistant as possible. This is what the registration rules still say.

  As breeders seeking to produce quality consistant breeding stock,we do cull for color.There is the St Thomas registry for the occasional excess color. This happens very rarely so is not a big problem. The great thing about raising sheep is that the lesser quality ones are still delicious or make good lawn mowers.

    Jo Swan