White markings should be of such distribution as to enhance the dog's appearance, but may not exceed one-third of the entire coat. They are not desirable on the flanks or on the back of the torso proper. On the face, white may replace part of the otherwise essential black mask, and may extend in an upward path between the eyes, but it must not be excessive, so as to detract from true Boxer expression.
BOXER Tummy Warmer Fleece Dog Coat Dog Sweater Dog - Etsy
Coat and colors
The Boxer is a short-haired breed, with a shiny, smooth coat that lies tight to the body. The recognized colors are fawn and brindle, frequently with a white underbelly and white on the feet.
Boxers with white markings covering more than one-third of their coat – conventionally called “white” Boxers – are neither albino nor rare; approximately 20–25% of all Boxers born are white
Hair is a horny, flexible, elastic filament. The part visible above the skin is actually the dead portion. Just as there are different breeds of dogs, there are different textures and distributions of hair. The length, diameter and texture of hair varies, as does its form (straight, flexible, wavy or curly). The location of hair on the dog varies as well. There can be a forelock on the head or a mane on the neck (as in the Chow Chow). A feathered coat has long feathers on the backs of the limbs, under the belly and on the tail; while in a tufted coat the hairs of the tail are longer than those on the rest of the body.
Many factors influence hair characteristics, including age.
As a dog ages, its hair turns gray, especially on the head, beginning with the muzzle. An undernourished dog or one in poor health, has dull, brittle hair.
A dog’s hair grows continuously. Hairs are replaced by shedding, which usually happens during a period of four to six weeks in the spring and fall. However, shedding is essentially constant in dogs that live indoors.
Smooth hair looks shiny and neat,
good winter coat? - Boxer Forum : Boxer Breed Dog Forums
Taking your muscular boxer for a shower can be quite challenging. However, if you have properly trained your dog, then it will not be a big issue. Depending on how much time your boxer spends rolling around outside, your boxer may need shower as much as once every month. You need to make sure that the water is not too cold or too hot for your dog. To clean your dog’s coat, you will need to buy a dog shampoo. Do NOT use shampoo for humans! After wetting your dog’s coat, gently apply shampoo on its coat, and make lather. Do not pour the shampoo on your dog’s face. Once the whole coat is covered, rinse off the lather using warm water. After the dog is properly rinsed, take a soft towel to dry it.
I live in Massachusetts and don't believe in dog coats for boxers.