Interesting links, thanks. The one about the chromatic scale references external measuring by spectrophotometer, as opposed to the self-reported one about UV reactions. Googling "spectrophotometry skin color" turns up stuff like this abstract http://www.ncbi.nlm.nih.gov/pubmed/20637000 talking about measurements for evaluating "pigmental skin diseases and scars." There's probably anthropology in there too later but I also need to stop this now. =>