I would liken it to sunlight, which, thanks to its specific wavelength, is visible to the naked eye. Various wavelengths of visible light are interpreted by the human brain as colours.
When sunlight falls on a glass prism, it breaks into the full spectrum of colours and reflections and instead of the white colour of the falling light we can see a colourful rainbow.
Why the visual perception? The light spreads very fast and the eye catches most visual perceptions. And eye is the largest information reader. The greatest information flow surges through an image.