Good example and discussion.
My red would tend to be a red — darker with some blue in it. Others might want a red with a little orange in it. Makes a big difference.
Or a person with red/green color blindness might be seeing a shade of gray, but calling it red because he’s been told, “That (shirt, car, ball) is red,” all his life.
This kind of thinking leads some people to the erroneous concept that there is no “objective” truth about anything. However, much of the time that’s a denial of what can be clearly shown, as in Bigg Redd’s example of the using a spectrometer to define accurately the light we’re describing as “red,” ... or in the case of the observable scientific fact that the union of sperm and egg creates, at that moment, a unique, living, human being.