The physics they share
A frequency is a rate of repetition, and both sound and light are repetitions. A membrane vibrating six hundred times a second and light cycling four hundred and thirty trillion times a second are doing the same kind of thing at wildly different scales.
That shared structure is worth understanding because it explains why pitch, colour and geometry can be discussed using the same vocabulary. It is a genuine parallel, not a metaphor.
The visible range
| Colour | Wavelength | Frequency |
|---|---|---|
| Violet | ~400 nm | ~750 THz |
| Blue | ~450 nm | ~666 THz |
| Green | ~530 nm | ~566 THz |
| Red | ~650 nm | ~461 THz |
Every one of those frequencies is roughly a trillion times higher than the highest note anyone can hear. The gap is the important fact here, and it is why audio-to-colour mappings are always constructions rather than correspondences.
Where the mappings come from
Colour-to-note tables go back centuries and were assigned by association. Green became MI because of a medieval colour-note association, and the solfeggio scheme carried that forward. The internal logic is that a note is assigned to a colour that feels related to it, which is a defensible creative decision.
That is not a criticism of the system. Plenty of durable creative frameworks work this way, by organising associations into a consistent structure so that decisions can be made quickly. The failure is only when a mnemonic that helps you decide becomes a claim about what is actually happening.
The gap that makes it interesting
The eleven orders of magnitude between the two ranges is not a curiosity. It is the reason the comparison can be made at all. If the frequencies were close together, the ear would perceive them as different versions of one thing rather than as two separate phenomena with separate descriptions.
It also explains why the comparison illuminates both. Talking about sound becomes more precise when you have a second example of vibration in a completely different register, because anything you say has to survive being true in both cases. Frequency as a rate of repetition holds cleanly; wavelength as a physical size does not translate between them without care.
Using it as a production tool
The useful version is compositional. Pick a palette, derive the harmonic material from it, and let the constraint generate something you would not have arrived at otherwise. Then judge it on whether it is good, and discard the rule if it is not.
A concrete version of that works well: choose three colours, find three intervals from the scale that feel right, and treat those as the vocabulary for the whole piece. Restriction of that kind tends to produce coherence more reliably than an unstructured search through options.
The mapping also works usefully in reverse. If a section of a piece feels too resolved, move its harmonic material to a contrasting part of the spectrum rather than rewriting it. Changing the colour changes the feel without requiring a different melody, which is a faster route than it sounds.
What will not work is expecting the result to surprise you physically. Nothing in the arrangement changes because a colour name is attached to it. The mechanism is entirely your own decision-making, which is a real and sufficient mechanism, just not a mysterious one.
The bottom line
Sound and light are both vibration, which makes the comparison genuinely instructive. It does not make them interchangeable, and the popular colour-to-note tables are inventions with a useful feel rather than discovered correspondences. Use them as a creative constraint if they give you ideas, and ignore them if they do not.
Try the mapping in a scale you already know
432Hz MASTER moves the whole set of tones at once, so a colour-to-note assignment stays internally consistent when you transpose.
Frequently asked questions
Is sound just light at a lower frequency?
Both are mechanical or electromagnetic vibration travelling through a medium, so the comparison is fair at that level. They differ in how they propagate and how humans detect them, and the useful similarity stops well before the two become interchangeable.
What frequency is visible light?
Roughly 400 to 700 nanometres, corresponding to frequencies of about 750 terahertz down to 430 terahertz. That is many orders of magnitude above anything audible.
Are solfeggio colour assignments real?
They are traditional and mnemonic rather than physical. They are useful as a system for organising ideas, and misleading if treated as a measurement of how sound relates to light.
Can I actually use this?
Yes, as a compositional constraint. Assign each section of a piece a colour and derive the palette from it, then check whether the result is better than what you would have written without the rule.