"Skin tone" refers to the color of a person's skin, which can vary from light to dark based on the amount of melanin in their skin cells. Full definition
As they apparently didn't dark brown for skin tone back then, they used blue. (religion.blogs.cnn.com)
Each of these models did particularly well with skin tones and color balance in actual photos, although neither one quite nailed the balance in our color - bar shot. (pcworld.com)
I noticed a more even skin tone even the day afterwards. (theeverygirl.com)