Is there a way to convert a color to a sound? Does orange in particular have a kind of Hz/audio equivalent other than 5e+14?
Yes, you can convert color to sound.
No, orange doesn't have a particular frequency or sound. You can pick whatever mapping you want. Do you want orange be a specific sine frequency, or should it represent a square wave? You pick.
Spectrograms often use color to represent the amplitude of a frequency component. Software like Adobe Audition will do the inverse function to convert an image back into a sound.
I've been trying to go the opposite direction, using audio frequency content to determine color of a waveform:
This is the same method used by Freesound.org, using the spectral centroid of the sound to produce a monochromatic color, but shaded to try to show the density of the samples as well as the peak amplitude.
What I'd really like to do is map the spectrum of the sound onto the spectrum of the color, so a low frequency sine would be red, a high frequency sine would be blue, and a combination of both would be magenta. Last time I messed with it, I was trying to figure out a way to weight it so that logarithmic sine sweeps look like a rainbow, white noise is white, and pink noise is pink. I'm not sure if it's possible, though, because of the conflict between linear and logarithmic frequency axes.
You can also take a look to Sonic Visualiser at: http://www.sonicvisualiser.org/
and also following the lead take a look at spear, a really cool app for visualizing sound in a different way:
If you search the web you will find much conflicting information on which color is what pitch... If you take A = 440 Hz and keep doubling and doubling until you get into the range of light you will find ROYGBIV = F, G, A, Bb, B, C, D, E, F. Try it yourself.
Just the tip of the iceberg.
On a somewhate related note, there was a great article or lecture I read once from Walter Murch talking about sound in terms of color. Only reference I can find of it now is here: http://bit.ly/dumkrz
If anyone knows where that article is, please let me know! (Thought it was on filmsound.org but couldn't track it down...)