Artist Neil Harbisson is completely colorblind, so he sees in black and white. But he still perceives color. Harbisson has an implant in the back of his head that's essentially an antenna with a color sensor attached. The sensor signals are transposed to audio and he listens through bone conduction.
Watch in the short video below, where he describes it as feeling a sort of energy.
Harbisson also gave a TED talk in 2012 where he goes into more detail about how he hears color, and at the beginning you can hear what he does. Because his vision and hearing kind of meld into one experience, it also works the other way around. Voices “look” like certain colors, and instead of dressing in a way that looks nice to him, he dresses to sound nice.
On top of that, Harbisson added infrared and ultraviolet perception after he was done with the color wheel.
That is, well, unperceivable.