I had a friend ask me this today, and I was stumped. Now I am not the brightest bulb, but I know there are plenty on here a lot smarter than I am, so have at it, please describe to me a color you've never seen!

this is the most profound question ive ever been asked...i legit have no answer....

I suppose there are colors beyond the visible spectrum which we are unable to see with human eyes, such as those in the UV.

I would describe such a color as invisible, as we can only see a narrow spectrum of visible light.

It's not really possible, since we can't see it. You can't relate it to anything, because you don't know where that color shows up. It doesn't have a name. It's not possible.

I wonder how a person with synethesia answer this question. As the same stimulus might produce multiple reactions.

This is hard.

Same, even people with synethesia disagree with each other

My original question has always been "What color is empty space?"