In T-America, many of the midrange vendors of makeup and clothes will offer a "nude" range with this kind of construction. (To them, "nude" doesn't mean "Caucasian average color" it means "your skin tone.") It's also what medical vendors offer as standard options for skin-tone prosthetics. Many people who can't find a match on the basic sets of five or ten tones can find one here. Beyond that usually requires custom matching, although some high-end makeup companies have a hundred or so standard shades.
EDIT 3/31/20: These are some sets I use for skin color words, organized by alphabet and by gradient.
You can also set up gradients for other colors than standard human skin.
Art exercises for skin tones are here.
This set of Olympic athletes shows great variety in body shape as well as skin tones.