In the 1980s, my friends in college and I played the Star Trek role-playing game. We had to create a sufficient backstory for each race. For the Andorians, we speculated that the blue skin had nothing to do with the color of their blood (which we denoted as iron-based, like humans.) Instead, we explained their complexion as the result of blue skin pigment, which is helpful in reflecting short-wavelength light rays, which we imagined are more intense on Andor than on Earth, because of a thinner ozone layer on Andor. (We did not call the planet Andoria.) Their hair is irridescent white, reflecting all light wavelengths more effectively. We originally envisioned Andor as a planet of extremes -- large, thick ice caps at the poles, with a geothermally active equatorial region. I have since modified the background info for recent STRPG campaigns to more closely match the canon that Andor is a large moon. I have it encircling a comparatively small gas giant. This allows for Andor to have a relatively close, fast orbit around the parent planet with nearly zero radiation from that gas giant. This gives Andor both starshine and shade in slightly less than 72 hours. At the same time, that close orbit generates some significant gravitational flexing, providing the aforementioned geothermal activity, mostly in a belt around the middle of Andor. The "shady side" (tidally locked to the parent planet) is ice-capped but gets some lateral starshine as Andor approaches and advances past the umbra and/or penumbra cast by the gas giant, so no point receives eternal darkness. The "sunny side" of Andor is a desert that undergoes soaring temperatures that approach boiling point during the more direct illumination by the parent star. The band or region in between is a mixture of geothermally heated pools and seas interspersed with temperate forests toward the shady side, and tropic-like forests toward sunny side that give way to a ring of semi-arid grasslands along the way toward the desert. Andorians have primarily colonized the temperate belt and the arctic region, both of which have an abundance of water (or ice,) and these regions afford easy tunneling to form living space.