A tan symbolized, like white sneakers, crew socks, and polo shirts, that one had the leisure for sports. A brown, svelte swimmer no longer carried the stigma of a dark wench. I suspect that this shift is only temporary perturbation of the whole complex of the human neotenic. Though these changes in our values often appear to be erratic through history I suspect they follow definite patterns. A change in style, cosmetic habit, or the ideal figure, though superficial and arbitrary on the surface, may be deeply tangled in the zeitgeist and tied even more deeply in our biological values about appearances.
Skin colors can change rapidly by varying the amount of blood in the skin.
There seem to be three themes in the evolution of human communication through flushing the skin with blood. The anger flush is an old tradition used today by many non-human primates. It is far from vestigial in humans, but there is considerable variation in its expression among human subgroups and within them. Physicians often refer to flushers and blushers as vascularly unstable. In groups without very dark pigmentation it is common enough to be generally recognized as a signal of internal mood.