the dyes can have an outcome as you have said, but we did mention that this was also due to the oils. when we started manufacturing what we called colour-charged waxes 5 years ago - we had seen results from aligning the raw ingredient colours with the colour of the paint, and the subtle enhancements.
it actually goes a lot deeper than this though, as the actual wavelength of the colour of light reflected is what causes the eye to perceive depth and wetness. this is why it is not possible on light colours - as more of the full spectrum of light is reflected, the eye does not log a change in the wavelength from ambient sun light and the reflected light (sunlight is actuall white light not yellow but due to atmospherics - i could go on). as the colour reflecting the light becomes darker, all the rest of the light spectrum is absorbed and only the colour seen is reflected. {breaks out a prism and plays with rainbows....where was i}
as the darker colours reflect different wavelengths then the full spectrum of white light, the eye perceives a difference and this is qualified in human terms as depth and wetness.
i have never tested or even seen this wax so i will and can not comment on what it would look like on non-black cars. however, if it uses much the same colour-charging chemistry we do - it can be used on any colour car, but would loose its dark (black paint) enhancement.
p.s. if it has some 'black-fillers' then it could potentially leave black swirls on non-black cars. now that might look seriously spidermanmobile.....