The question of when to refer to someone's skin tone is one I struggle with. It seems to me that if we could get in the habit of thinking of people's physical descriptions as including a range of skin tones, so that I can describe myself as 'olive-skinned' (the old-fashioned term for my complexion) or some other term that indicates that I have dark-ish caucasian skin, then it's not singling someone out to refer to their skin tone,.