The scenario is as follows: a habitable planet is being colonized. The conditions are fine, in spite of differences in the parent star. The star is smaller than our sun, either an orange K-star or a red dwarf M-star. You may assume two scenarios:

  1. a planet orbiting a K-star with a normal day and night cycle, not too different from Earth, so humans may adapt. Colors may appear as though looking through Polaroid sunglasses, shifting towards yellow and orange.

  2. planet tightly orbiting an M-star. This means tidal locking. Sun appears fixed in the sky. Timekeeping is essential to maintain the circadian cycle of the colony as a whole, and the sky would be rich in red at all times. Assuming the habitable areas are at the twilight, the colonists will experience the view and colors of perpetual sunset.

I have found these colors appealing, and I like wearing the Polaroid sunglasses for the visual effect. However, I am unaware of their effects if they lasted for the whole day. Does the shift from mid-day blue to sunset colors have an effect, or is it just the length of the day that counts?

  • $\begingroup$ Psychological effects strongly depends on the history of the individual, without even considering the difficulty of finding two psychologists to agree on something. I am not sure this can get an answer. $\endgroup$
    – L.Dutch
    Aug 25 '18 at 9:21
  • 1
    $\begingroup$ The human visual system has an excellent built-in automatic white balance correction mechanism. Colors will not appear noticeably shifted. Remember that color is a sensation which exists in the mind, not a physical quantity. Try to think of a spectacular sunrise or sunset which you have experienced, when the sky appeared gloriously red: did you notice a makred change in the colors of the objects around you? Or remember the days of incandescent light bulbls; those put out a very orange light, so much that we needed special photographic film: yet to us humans colors were just fine. $\endgroup$
    – AlexP
    Aug 25 '18 at 11:00

Light temperature and color is not the only thing influencing our biological rythm, but it plays a major rule.

The orange hues at dusk cause the production of melatonin, the "sleep hormone" while blue hues at morning cause melatonin to be blocked. If you don't have a change in hues, the melatonin production might go on during the day, although on a smaller level.

More important than the hue of light is the quantity. Our eyes are so good at adapting that we don't see too much difference between indoors and outdoors, but the intensity of light outdoors is ten times as high as indoors. Exposing the skin to light also aids in the production of vitamin D.

The effects of humans living in either of your scenarios would probably include:

  • Feeling tired or drowsy during the day if not exposed to artificial light or melatonin inhibiting chemicals. Humans would have problems concentrating and do more mistakes than when highly awake.

  • Higher sensitivity to strong lights.

  • Problems distinguishing colors the way we do on Earth (they simply look different) and possibly problems distinguishing sharp edges and lines due to lower contrast. Script must be printed in a bigger font to be comfortably readable.

  • Insomnia on the tidally locked planet unless light is blocked by artificial means to create a night cycle. Humans tend to prolong their sleep cycles if no indication of time is given.

  • Lack of vitamin D unless supplemented to food. A very different diet might cause more severe malnutrition.


Human's have many many many ideas and opinions about the way colors effect psychology. However, all in all individual preference plays a big role in what colors make an impact.

I think the most memorable color scheme I know is "the pink locker room" which entails a sports team coloring the visiters locker room pink to lower moral. https://www.thoughtco.com/pink-locker-room-at-iowa-kinnick-stadium-791834 However, the effects are very much ancedotal and may or may not be an indicator of color's effect on human psychology.

The only thing I can tell you for sure is that humans hate change, so the new environment may be slightly stressful for colonists, especially considering an estimated 35% of humans prefer the color blue the most.


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