Tan is the increase of Melanin in your skin.
My Dog Has Little Red Puss Filled Pimples All On Her Belly Side, What Could This Be? They Do Not Seem To Bother Her At All.
Could be Acne or from where she rests. Could be Bacterial and should be checked by a Vet.
The More the better. If she wants to then don't hold back. Keep in mind she might not always want to depending on her physical or emotional feelings, but don't let her be the one who always decides When and Where. You have needs too.