hemoglobin, as any pigment, absorbs light at a specific wavelength. chemically, it looks very similar to clorophyll, it just has an iron atom in it's middle, instead of clorophyll's magnesium.
being red, one would guess it's light absorbtion spectrum would be a deep green - that would explain why we 'feel' so good in the forrest
also, the iris pigments absorb light at specific wavelengths, irises being kind of our own solar dishes

; also the hair's colour transforms harmfull UV into heat, and probably has some other effects too. that would explain why we have so many hair on our heads (next to our brains), and why yogis never cut their hairs (they say it's their antennae to knowledge).
many organo-metallic compounds absorb and emit light, the metallic atom acting as a kind of 'antennae'. that also makes sense from an alchemical point of view, as alchemists tried to 'capture the metallic luster' (gold being the preferred element in this quest).
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