I composed a piece in 1975 called LASSOED RAINBOW for an installation at the De Young Museum in San Francisco. It was a series based on a chart of sound / color analogies in an issue of “Scientific American”. If you take the light-wave frequencies of the visible spectrum and shift them down 20 or so octaves, you can make correlations. For example, green would be middle C. It’s very subjective of course; what sounds green to me may be totally different for someone else, but here is the way I mapped the underlying drone of each piece:
That completes the visible spectrum, but I added an eighth piece, BEYOND ULTRAVIOLET to complete an octave with F#.