[Ms_P]

Is she still a puppy?
Chis do go through a skin color change, I think it is somewhere around 3 to 4 months. I don't remember exactly.
If your puppy isn't showing any signs of distress, excesive itching or hair loss, then I wouldn't worry about it.
Mention it to your vet on the next visit.

 

[Ms_P]

Could it be sunburn?
Is the other dog getting a little rough?
She seems a little too old for the skin color change.
But she's not itching or anything.
I would call your vet tomorrow and ask them.