Every color has a different meaning!
black
Dogs, like us humans, have melanin in their skin, but because there is no hair in this part of the nose, more melanin is needed to resist the damage of ultraviolet rays to the skin, so most dogs have black noses. This is a normal color.
white
Refers to the part of the nose that turns white and black. Because melanocytes are missing, there is no way to deposit melanin, so it turns white. The reason for this loss is mainly due to genetic inheritance. For example, some people have white skin, some people have black skin and some people have yellow skin. This is a genetic defect, but it can't be said to be a disease, because this defect will not make the dog uncomfortable except for affecting the face value.
Red (brown)
The color of the dog's nose changed from black to red. Although melanin deposition decreased, it may also be caused by external conditions. For example, unbalanced nutrition intake, skin diseases, trauma, lack of sunshine and so on. The solution is simple, that is, supplement nutrition, increase sunshine time and supplement nutrition.
grey
With the increase of age, the metabolism of dog organs and bodies will slow down and their functions will deteriorate, and the melanocytes in the nose are no exception. Their transformation and metabolism functions are much worse than before. If melanin is not completely metabolized, the dog's nose will turn gray, and peeling and cracking will occur. There is no good solution at present. What pet owners can do is to delay the aging of dogs.