[labster]

The color wheel doesn’t really wrap around. We just take a cut of the visible spectrum, and overlay the red and the blue ends. We don’t perceive periodicity in light; near infrared is not one octave lower than violet light. The color range we see is just one that happens to be most useful in a nitrogen/oxygen atmosphere under a Class G sun.

[cwmoore]

So it happens that we can hear several octaves in sound, via pressure waves, where a note an octave higher or lower is defined as twice or half the frequency, and when the "same note" in different octaves are played together the sounds are full and noticeably harmonious.

The range of the electromagnetic spectrum we see is indeed very close to "an octave" if defined as the doubling of frequency, but it makes no particular sense to consider the harmonies of octaves of visual light when there is only one of them.

[e7b9]

What about intervals within the octave of light?

[lioeters]

About intervals within the octave of light..

The first thing that came to mind was "complementary colors", which are two colors opposite each other on the color wheel.

> They create the most contrast and therefore greatest visual tension by virtue of how dissimilar they are.

- From https://en.wikipedia.org/wiki/Harmony_(color)

This is like "tritones" in music, which are two notes with an interval spanning six semitones. If there was such a thing as a "note wheel" with a circumference of an octave (12 semitones), two notes that form a tritone are opposite each other on the wheel.

---

There are "split-complementary colors".

> Split-complementary colors are like complementary colors, except one of the complements is split into two nearby analogous colors.

> This maintains the tension of complementary colors while simultaneously introducing more visual interest with more variety.

..And "analogous colors", three colors that are next to each other on the color wheel, and a tertiary.

A musical equivalent of these might be like different types of chords.

---

Also, there are "triads", like primary and secondary colors.

> Art education materials commonly use red, yellow, and blue as primary colors, sometimes suggesting that they can mix all colors.

> A secondary color is a color made by mixing of two primary colors in a given color space.

[taejo]

Red and *violet ends. But why do purple and violet look the same?

[mkl]

A quirk of human vision. Our "red" cone receptors in our retinas are mostly sensitive to redder hues, but also have a bit of a bump down in the violet part of the spectrum. This shows some graphs that sort of explain it: https://physics.stackexchange.com/questions/433119/why-does-...

However, such spectral sensitivity graphs vary a lot (perhaps because people's vision does, but also they'll be measuring things differently): https://duckduckgo.com/?q=retina+cone+frequency+response&atb...