Color of nose in dogs can be of liver color, black, or of coat color depending upon breed. There are few reasons of change in nose color of dogs that can be normal and sometimes abnormal. Dogs have an enzyme called tyrosinase that is responsible for pigmentation. Function of this enzyme can be affected by temperature. Its function is reduced in old age and cold conditions resulting in to loss of pigmentation. This is possible explanation of snow nose or winter nose that is more common Labrador Retrievers and Golden Retrievers.
Some illnesses and allergic reactions can also cause change in nose color. These are trauma, abrasion, contact dermatitis etc. There can be many more reason but change of nose color in dogs still needs research. If your dog no other signs of illness but only changed nose color then no need to be worried. Remember, pink noses can develop sunburn and cancer. You can apply sunscreen to avoid these conditions.
Some illnesses and allergic reactions can also cause change in nose color. These are trauma, abrasion, contact dermatitis etc. There can be many more reason but change of nose color in dogs still needs research. If your dog no other signs of illness but only changed nose color then no need to be worried. Remember, pink noses can develop sunburn and cancer. You can apply sunscreen to avoid these conditions.