Boxer's Standard mentions two colors as being acceptable - red (fawn) and brindle (striped). In fact there is only one color in Boxers - red, and brindle is simply a striping pattern. Think of two apricots. If you cover one with a black veil, the black mesh will cover and "hide" the apricot's true color. Even though our covered apricot looks different now, it is still the same solid red fruit. It is similar with Boxers: a red Boxer is a "naked" apricot, a brindle Boxer is the apricot "dressed" in black veil. The tighter the mesh of the veil, the less ground color is visible. If we cover the apricot with a yashmak such as the one Muslim women use to cover their face, our juicy fruit will appear totally black. The striping of a brindle Boxer can be so intense, the dog will appear nearly black.

The existence of brindling or the lack of it in each Boxer is determined by the two genes the Boxer got from his parents. Each parent contributes one gene. "B" gene means brindling (covered apricot), "b" gene means no brindling (naked apricot).

A Boxer can have either two "B" genes, two "b" genes or one of each kind. When one of the sire's genes meets one of the dam's genes in a newly created puppy, they determine his final color. If both of the parents' genes were "B", the puppy will be brindle. If both of the parents' genes were "b", the puppy will be red. If one parent contributed "B" and another one shared "b", the puppy will always be brindle, because "B" dominates "b". Think of it as "B" gene being bigger and stronger and always winning over "b" gene when arguing about which one gets to be exhibited phenotypically in the puppy.