• One habitable world in each system (blue sun system and yellow sun system).

  • The two worlds are fundamentally Earth-like.

  • The native humanoid species on each world are genetically compatible.

  • A native of the blue sun system visits the world in the yellow sun system.


Would the blue-sun-alien perceive light on the yellow-sun-world in the same way the yellow-sun-native does?

  • 2
    $\begingroup$ Color is a sensation which exists in the mind; it is not a physical quatity, it does not exist in nature. The relationship between the physical properties of light and color as perceived by a human standard observer is complicated, and depends both on the spectral composition of the light and its spatial distribution. It is very highly unlikely that two different species of the same world would perceive color identically. $\endgroup$ – AlexP Jan 6 '18 at 11:47

It might depend on if your natives are human and just live there over several generations, or if they took a different evolutionary track.

On earth, being able to pick out camouflaged creatures is actually EASIER if you are colorblind. This is the reason why South American primates tend to be colorblind.

It might not just be about lighting either. It might be about environment. Here on earth green environments are the norm, so we adjusted for that.

But on your blue sun planet, it might be a different story:


Because of this, natives from the yellow sun system may have different advantages than blue when they switch worlds. It might be possible that one or the other may be considered to be "colorblind" on the other planet, and this may confer advantages and disadvantages respectively.

The races might be genetically compatible, but even here on earth, there are differences from person to person. And it's been postulated that we don't even see color the same way from person to person.

For example, you and I are taught that a particular shade is "red." We may, in fact see slightly different shades, but since we both know THAT shade as red, we both call it the same thing.

When it comes to red-green color blindness, it's more marked. For hunters tracking prey, not being able to see the difference actually makes those who are colorblind in that way better at picking out animals. This may be why, if men were the main hunters and women the main gatherers, more men experience colorblindness of this kind, and more women can see differences in shades (because this was more important when it came to judging ripeness when gathering).

Those on the blue planet might even see differences in color that the yellow planet folks can't and vice versa--so natives of either may consider most of the population of the other planet colorblind. Because there is a lot more to the spectrum than we can see, and there are even animals on this planet that do not see what we can, but can see colors we cannot readily perceive.

While you may believe that because they are genetically compatible that your two populations will see colors in the same manner, consider this fact: within our own population there are differences in how we see color, even when people are genetically compatible. Take that to two different planets, and there may be even more of a difference.


If you have ever had to fight with lighting in a video studio, you will know the frustration that ensues because your eye is self adjusting for white balance. When you look at he scene in real life, whites are white. Look at it on the video monitor, and everything is red because of the tungsten lights.

After an adjustment period (a few minutes to a few hours) your visitors would perceive colors exactly the same as a native.

  • $\begingroup$ ...unless they’ve evolved to have different sets of cones to cope with the different lighting... $\endgroup$ – DonielF Jan 7 '18 at 6:38
  • $\begingroup$ If the pigments in the cones are different, , any cross population offspring would have vision problems, which I take to violate OP's initial premise of genetic compatibility (although he will have to weigh in on that). $\endgroup$ – pojo-guy Jan 7 '18 at 13:19

If the humans have the same structure in their eyes, which can be assumed by the fact that they are genetically compatible, the color of the sun should have no effect on their perception of the world.

There might be cultural differences based on what colors are significant important on either world. But that affect is more a function of culture/language than it is a function of the star itself.

For example in English we have consider red and pink to be distinct colors. While other languages don't consider pink to be a distinct color and would refer to the colors we call pink as light red.


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