(S) Solid in color showing no white or only a small spot of white on the chest, blaze or toes

(Si) Irish Spotting/Tuxedo - Showing white on the chest, leg boots, toes, blaze or tip of the tail. Amount of white can vary and may not appear in all the above areas.

(Sp) Piebald - Appears as circles or patches of color on a white background. The patches are variable and more or less can appear all over the dogs coat. Sometimes the patches of color connect leaving a large saddle pattern on the dog.

(Sw) This gene will turn the dog a solid white color but will sometimes leave some color on the ears, tail, eyes or top of the head. 

How White Genes Combine
Example
The following section will give examples of how a dog will look if crossed with a dog that has two different alleles at the (S) Loci.
(S) Crossed to any (S Series) gene si, sp or sw will produce a solid colored dog that does not have any white on the coat. The (S) gene does not let any white color to develop on the dogs coat. Sometimes there is a small spot of white color that will appear on the dogs chest.

Shown below is the (si) gene which produces varying degrees of white on the coat but never allows the color to break up into the piebald (sp) pattern. These patterns may include a white chest, blaze, collar, boots or socks and tip of tail.

The sp gene (piebald) also shows itself in varying degrees but breaks up the color into patches of  designs on the dogs coat. A piebald dog can be from almost solid white with color only on its head and near the rear to a completely broken up fancy pattern all over.