We used the approximation that the hypodermis was a perfectly white reflector; so the thickness wouldn’t matter. The collagen fibrills scatter light in such a way to create a yellower tint. So a person’s skin might appear this way in the absence of melanin and haemoglobin. I’m not an expert on population statistics, and so cannot give an opinion on specific skin types. Everything was based on ranges.

There is a separate effect of increased bilirubin content, that would appear if someone was ill.