The horseshoe shape is a little harder to explain;
Noooo that’s like the most interesting and fun part of it! And it’s actually kind of easy to explain why it’s a tongue shape: if you plot “colors of the spectrum” or like “all the colors a laser can be, or a single photon can be” on this plot, it makes some curve, right? And then all the colors you can possibly see* are exactly the convex hull of those points, which means you draw a straight line between the two ends of it which represents all the most saturated possible pinks and purples. They work differently from the spectral colors of the rainbow because there’s no such thing as a purple photon.
The tongue shape is beautifully descriptive of the underlying reality. You immediately get subtle truths like:
Yes there’s a closed curve of all the most saturated colors, like a color wheel
It’s not actually symmetric like a circle because there’s this one part of it (the pink/purple/magenta line) that’s special
*In normal static lighting conditions, so not counting “impossible colors” you can get with afterimages or some other weird hacks.
Noooo that’s like the most interesting and fun part of it! And it’s actually kind of easy to explain why it’s a tongue shape: if you plot “colors of the spectrum” or like “all the colors a laser can be, or a single photon can be” on this plot, it makes some curve, right? And then all the colors you can possibly see* are exactly the convex hull of those points, which means you draw a straight line between the two ends of it which represents all the most saturated possible pinks and purples. They work differently from the spectral colors of the rainbow because there’s no such thing as a purple photon.
The tongue shape is beautifully descriptive of the underlying reality. You immediately get subtle truths like:
Yes there’s a closed curve of all the most saturated colors, like a color wheel
It’s not actually symmetric like a circle because there’s this one part of it (the pink/purple/magenta line) that’s special
*In normal static lighting conditions, so not counting “impossible colors” you can get with afterimages or some other weird hacks.