I will try to make it somewhat easier to understand how color genes work and what colors your puppies could be depending on the colors and genes of the parents.
Pure Sable (SS)
carries two sable genes
Bi-Factored Sable (SB)
carries one sable gene and one bi-black gene
Tri-Factored Sable (ST)
carries one sable gene and one tri-color gene
Pure Tri-Color (TT)
carries two tri-color genes
There are also Bi-Factored Tri-Colors (TB)
(they do not look different from a Pure Tri-Color)
carries two bi-black genes
Modifiers are genes that modify the outward appearance of the base coat color.
The two main coat modifiers in the Sheltie breed is the merle gene and the white-factor gene.
The merle gene; mottles and lightens the appearance of the base coat color. Based on past research it was throught that breeding two merles together could always cause health issues and instances of death, but there has been some new and exciting research done on the merle gene recently. Research has shown that there are actually 6 variants of the merle gene and that not all variants can, or will, produce Lethal Double White offspring that can have hearing and sight loss. I HIGHLY recommend that anyone that may be interested in breeding merles visit and become a member of this Facebook group and purchase Mary Langevin's book.
The white-factor gene; determines the amount of white on the mainly the main part of the body.
Many people are misinformed that the white-factor gene, and most often dogs carrying
two white-factor genes (color-headed white) are the same as, and/or, have the same health issues
as a double merle. This is absolutely inaccurate.
The white-factor gene PRODUCES NO HEALTH ISSUES.
Dogs that carry the white-factor gene have no health issues that are not otherwise
found in another or regular colored Sheltie.
Sometimes it may be difficult to tell the difference between a color-headed white dog and a double merle, as you can have a color-headed white merle. One way to tell is the color of the eyes. ONLY MERLES can have blue or mottled/merled eyes, but they don't have to. Another way to figure it out is look at the color of the parents. A double merle can only be produced from the mating of two merles. ALSO, new research has shown that the merle gene, depending on which merle type it is, CAN be a hidden gene. new research has shown that there are, in fact, 6 variants of the merle gene.
Sable base color with one merle gene
Bi-Black base color with one merle gene
White-factored (carries one white-factor gene);
Notice the large collar, all four white legs with the white going up the stifle of the back legs, that are connected by an excessive white belly.
Tri-Color base color with one merle gene
Double Lethal Merle combination
Carries two merle variant genes that can cause blindess and deafness if paired together.
*Not all merle variants will/can cause this to occur*
Color-Headed White (carries two white-factor genes);
Notice the excessive white coloring that covers
most of the whole body of the dog.
Please note: color-headed white are dogs with more than 50% of their body covered with white. It actually has NOTHING at all to do with the color of the head. They can have no color on their heads at all
and are still considered CHWs.