There are several previous questions on this group regarding blue skin but none of them fit the needs of my world.

I need to allow a group of very pale skinned aliens (albeit with typical mammalian physiology) to become blue reasonably quickly. They are identical in all respects, except the blue skin, to another group of aliens in whom blue skin evolved. The non-blue have to be able to pass as blue when they want to.

Turning blue could be by ingesting something, or by dyeing the skin. The method used should be something that is considered to be relatively non-toxic. I'd like to avoid the idea of a paint.

I vaguely recall reading the the ingestion of methylene-blue causes the skin to look blue but I have been unable to locate any source to verify the idea or to give any indication of its feasibility. Any ideas? Note: if it wouldn't be possible for an ordinary human in the real world to use the method, then it's probably not going to fit my world.

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    $\begingroup$ It doesn't matter. It's your world, you set the rules. The how and why of things happening is entirely secondary to the characters involved. Stop concentrating on the irrelevant minutiae of the world, and concentrate on its people. $\endgroup$
    – Ian Kemp
    Feb 28, 2023 at 10:45
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    $\begingroup$ The ancient Picts used tp dye their skin blue using a vegetable paint extracted (we think) from woad, Isatis tinctoria. (Them painting their skin blue is why the Romans calledf them Picti, meaning painted ones in Latin. We don't know how they called themselves in their own language.) $\endgroup$
    – AlexP
    Feb 28, 2023 at 11:41
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    $\begingroup$ @IanKemp it could matter. He seems to indicate that the characters might use the techniques to infiltrate something or use it in some way when impersonating the other race. Tying it to realism can add a bit to the story over just ramming something in randomly. $\endgroup$
    – Demigan
    Feb 28, 2023 at 11:43
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    $\begingroup$ If it's OK for your aliens to take years to develop blue skin, then check out Argyria. This would involve ingesting colloidal silver for some time. Once they do though, it won't be easy going back to their natural skin color. If you want them to blue and unblue themselves on demand, then paint seems to be the best option. $\endgroup$ Feb 28, 2023 at 13:59
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    $\begingroup$ @IanKemp --- I think this is perhaps not the most helpful approach. Yes, technically speaking, "it doesn't matter", it's her world, etc. But is that what we're about here? Just telling people that their questions don't matter? That our work and creativity in responding just doesn't matter? Just gonna say this straight out: this is not what our mission here is. If a querent wants to know how to get blue skin, then it becomes our job to help them get blue skin. End of story. If you don't want to help, then perhaps keep quiet so others can and so that new folks won't feel unwelcome here? $\endgroup$
    – elemtilas
    Feb 28, 2023 at 23:57

2 Answers 2



Indigo is a dye very close to primary blue, derived from several species of shrub. Your people culd have access to a similar shrub or other source of dye.

Indigo has been used for body ornamentation for millennia. This is considered safe, though full-body or facial use isn't recommended, though mainly for lack of knowledge of ill effects. I can't find any mention of how waterproof it is, but given that indigo is used for dyeing textiles, I Imagine that it isn't easily washed off. You problably need solvent or have to wear it off, like henna.

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    $\begingroup$ +1, this is also becoming common to reduce voter fraud. It's called "election ink." $\endgroup$
    – JBH
    Feb 28, 2023 at 15:44
  • $\begingroup$ Beautiful. Just like henna for red. $\endgroup$ Feb 28, 2023 at 23:31

The orange pigment in carrots can be concentrated in human skin cells. This means that if enough of a human's diet is carrots, their skin will begin to appear orange, similar to how a flamingo's diet makes it pink.

this effect is temporary. While the individual skin cells will always be orange, humans go through skin cells so quickly that any change in diet will cause the skin to rapidly return to normal.

An effect like this could work. It would only require a food with a pigment that the race can concentrate in their skin. It might even change faster if the race has skin that's suitably different from ours. Like, the layer of our skin that gives us our color is technically dead, so the method would need a lot of prep time for a human, but if your race has thinner skin like a frog, they might get a much more dynamic effect.

  • $\begingroup$ A nice generic approach to the problem. Good ideas. $\endgroup$ Mar 5, 2023 at 0:45

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