I noticed my chocolate lab has two different shades of brown.
In the summer, she turns a really pretty golden brown. Although it is partly because of the sunshine lightening the tint. Recently her winter coat has been coming in quite a bit darker than the summer coat. Really shiney, she has a beautiful coat. You can easily see the difference as there are a few spots of summer lightness around her shoulders.
I bathed and brushed her once since she started shedding for the winter coat (weird). It seems I caught it at the perfect time - her fur is great now. Her shed cycle must be complete. When she was in the tub, a lot of hair came out and thats all she needed.