Charlie is a yellow lab with black trim (that sounds funny but I don't know how else to say it). He's not a Dudley. His nose went pink in the winter, like it usually does but it hasn't gone black again???? I live in Southwestern Ontario Canada.
You are describing snow nose or winter nose which occurs in light colored dogs.* There are a couple of theories about why it occurs...among them loss of sunlight and vitamin B difficiencies. While younger dogs noses may turn back to black in the summer, most of the time it is permanent.
Murray developed a snow nose when he was 2. He's 5 now and you can see that it is still pink.
No worries. It usually happens to most yellow labs.
♣ Laura ♣
One of my yellow labs nose turns pinkish every winter. As the weather warms, it darkens again. The other yellow seems unaffected by the weatehr change.