About a month ago I finished building a number of boxes that appear to make light audible, for the experimental film maker Lynn Loo. The design was the classic example from the Forest Mimms Engineers Notebook, plus a couple of modifications to control the sound (very similar to the ones I built for the Self Cancellation event). These circuits are fun but they aren’t really making light audible merely making the intensity. Hence you can hear the scanning of an LCD screen or the mains hum of lightbulb, as the LDR in the circuit can “see” the light source switching on and off. Lynn plans to use them wth film where she has recorded various light sources on to a 16mm colour film.
A theoritical version would pitch shift the light spectrum into the audio frequency range. So that you could hear the difference between the colours.
The question to ask is “is it possible to detect colour?” The problem I think is that the The natural extention of this kind of thing would be to use