eyes
Sometimes I say something is green and Dr B. claims it is blue. Or the opposite, I can't quite remember now. I keep meaning to verify with his chequered duvet cover in several shades of green and blue, but whenever we are under it I get distracted.
The following are simulations of the way bitful is seen by people with Deuteranope (a form of red/green color deficit), Protanope (another form of red/green color deficit) and Tritanope (a blue/yellow deficit - very rare) colour visions.