I have been designing a species of elves with blue skin as one of their most striking features. I'm drawing inspiration from primates that also have blue skin. Think the scrotum of a vervet monkey, or the buttocks of the mandrill. According to this article,(http://jeb.biologists.org/content/207/12/2157.full), the color is caused by light scattering through special layers of collagen. This layer can be 800-1500 micrometers (0.8-1.5 mm) in the areas described.
As an adaptation to produce and support this amount of collagen, I'm giving the ability to synthesize their own vitamin C, a somewhat carnivorous diet, and a higher haemoglobin count to improve oxidation to the dermis. I'm considering having them sail and hunt in the ocean, since they would be effectively immune to scurvy.
However, Human skin ranges from 0.5 to 4mm in thickness, so my hypothetical elves may have much thicker skin. My questions are follows: what impact would having this thick layer of collagen in the skin be on the elves everyday life? Could there be deleterious effects? And finally, are the adaptations I have listed enough to combat the potential problems?
Edit: as far as ’deleterious effects'go, the ones I can think of would be stiffness in the face and possibly a higher likelihood of forming scar tissue, though feel free to suggest more.