Dumb theories; why are there white people?

So... I was thinking about color, for the purposes of painting. All humans are basically some flavor of desaturated orange, but not all hues show up the same way at different saturations and different values. Yellows (and by extension yellowish oranges) tend to show up better when brighter; reds (and by extension reddish oranges) show up better in mid-range darks. So if you're an Asian or Caucasian, your skin won't contrast as clearly with blueish direct or bounce light as an African-American with more reddish hue more clear within your skin tone.

Cool. So if you're living in a warm bright part of the world, having melanin is pretty obviously useful, but also, it's pretty evolutionarily useful to have pattern recognition from these big highlight areas on forehead, cheeks, nose and chin, which will bounce light. Conversely, if you're living in rainy-foggy-snowy Eurasia, melanin is kind of an eh for you, but it's evolutionarily useful to have pattern recognition linked to having dramatic shadow areas under eyebrows, nose, cheeks and chin in contrast to less dramatically colored forehead/cheeks/nose/chin. And if you have weird, funky, non-brown eye color, that'll just show up even better. There's really no reason not to select for being humanity's atypically colored children.