Science Buddies: "Ask an Expert"

This year I've developed an interest in cosmetology and some of the things I've found in my research are the different ways skin color is measured which seems to be especially important in testing topical spot removal creams, for example.
What would be the best method for analyzing skin tone? Is there an order for most to least cost-effective/accessible? So far I've found information on spectrophotometers, reflectometry, and visual scales like the Fitzpatrick scale.

Are there other, more consistent/accurate ways to measure skin tone (are any of these the best options)?

Hello, You have posted 4 very similar questions. The Science Buddies guidelines state that you should keep your questions about the same project together. This helps the experts here at Science Buddies to see all your questions in one place. Thank you!