the "visible spectrum" is conjured up of the only colors we can see. Technically speaking, xrays, gamma rays, radio waves, etc etc all have color, just not visible to our eyes. It is possible that many other animals or species might see colors we can't see, vice versa. Ultimately, the only way humans might see a "new color" is by the process of evolution. Freeze yaself, and hope brain transplants are coolio in the future, son.