# Can hair somehow shine in all colors of the rainbow?

This is Rainbow Dash:

I somehow don't like this design, because this suggests that RD dyes streaks in her mane, which seems to me contrary to her character traits.

Which is why I like this fan design:

This hints these are not dyed streaks. Rather, her mane, apparently naturally, shines in all colors of the rainbow.

Is it possible that her mane acts like a prism, dispersing the light and producing this rainbow effect? Or is it possible that her hair gathers moisture from air and the water droplets produce a literal rainbow?

The latter option would be especially nice, because perhaps, once her hair gathered enough moisture, it would allow RD to perform such a trick:

If this is impossible, what would be the required changes to how the nature is wired to make this possible?

• The hair could contain some sort of transparent prism material. – bob1171 Nov 25 '17 at 20:26
• Question- is this downvoted because something is wrong with it or just because it's a MLP-based question? – Friendlysociopath Nov 26 '17 at 4:04
• As this question is currently, it’s not technically about worldbuilding and is likely to be closed for that reason. I answered it because I think the title question is an excellent one and should appear in more fiction, but the entire body of your question is about a character that already exists in a world that already exists. – Dubukay Nov 26 '17 at 6:24
• @Dubukay it's absolutely about worldbuilding; it's a "creature feasibility" question, along the lines of asking how a werewolf can rationally shift. – akaioi Nov 26 '17 at 7:46
• @Dubukay but the entire body of your question is about a character that already exists in a world that already exists. This is an example so that others can understand what I mean. – gaazkam Nov 26 '17 at 10:33

What you are looking for is called structural color, and it indeed exists in many aspects of the animal kingdom.

Peacock feathers, for one, are structural color. They aren't actually a pigment, but rather an alignment of microscopic structures:

Butterfly wings are the same:

The color of the human eye is actually an example of structured color. The fine muscles of the iris refract light via the Tyndall Effect. This is why human eyes can look so different under different lighting condition. Structural color tends to be directional, yielding iridescent effects. These effects are, of course, perfect for your rainbow hair!

• I don’t actually think this is what the asker is looking for. Structural color isn’t something that would change hue based on the angle it’s viewed at, and that’s what I think the asker is seeking – Dubukay Nov 26 '17 at 6:18
• @Dubukay Structural color is something which changes hue based on angle. From the Wikipedia article: "The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively. Different colours therefore appear at different angles." – Cort Ammon Nov 26 '17 at 16:02
• True! I was mistaken about structural color, I apologize causing confusion. Great answer! – Dubukay Nov 26 '17 at 23:09
• @Dubukay: I don't think colors that change with angle are what the OP was asking for, but rather multiple colors, possibly iridescent. Which you could get by a similar mechanism to a peacock's tail, combined with local coloration sites that produce tiger stripes or leopard spots. I think there's a fundamental problem, though, at least with earthly biology. Most mammals are dichromats, and so wouldn't be able to really appreciate the colors. (Most are some variation on brown or grey.) – jamesqf Nov 27 '17 at 0:30

Your best bet is diffraction. This is a process in which incident light is split into its respective colors because different wavelengths of light are diffracted different amounts. What Rainbow Dash’s mane could do is act like a diffraction grating which would cause exactly this effect.

This isn’t even that far-fetched. Comb jellies already do this with their cilia and create rainbows that oscillate up and down their bodies. All that would be required of Rainbow Dash is that she has a mane made of very thin hair strands- something that’s probably already in canon.

Oil solves the problem. Have her genetically inclined to produce more oil in her hair than normal, and make the hair light colored (the closer to white the better). When light hits it at the right angle, you'll see it shimmer like a rainbow.

Note that I'm ignoring the health effects of higher oil, the need to regularly clean (oil gets dirty), and the exact nature of the oil. (We're talking fiction, are we not?)

I'm also ignoring the fact that you will never see the entire length of hair shimmer like a rainbow. Even straight hair curves with the wind and motion of the body. As that curve shifts across the sun, different sections of hair will shimmer. If you want a consistent solution, it must be illuminated.

Perhaps a strange suggestion, but could Rainbow Dash have fibre optic strands for hair? (If it’s any consolation, Amazon beat me to the idea... https://www.amazon.co.uk/Set-Extentions-Light-up-rainbow-Barrette/dp/B00C4BBTD0)

Fibre optics are generally made from silica, which occurs naturally in the skeletons of siliceous sponges, phytoplankton, and zooplankton, as well as in certain tree barks and some grasses. There have also been suggestions that silicon is beneficial for nail, hair, bone, and skin health in humans, so fibre optic hair could be an extension of this.

Fibre optic strands are near in thickness to human hair, so that wouldn’t be an issue. You may have a problem with the luscious long locks, but Wikipedia assures me that more flexible fibre optics are being worked on: https://en.m.wikipedia.org/wiki/Optical_fiber. Even so, RD could look pretty awesome with a rainbow Mohican.

The glossiness and sparkle in your images would definitely be achievable, given the illumination of RD’s mane and tail. Either RD could produce this effect in short bursts, with a charge like that of an electric eel, or otherwise have enough background electric energy to keep her lit up. The more happy/excited/energetic RD gets, the more brightly her hair would shine.

• A nice one, though in my imagination her hair can't produce light itself, as in yours it apparently can. Still, +1. – gaazkam Nov 25 '17 at 21:03