How do you explain "color" to a kid?

I was sitting at circle time with the kids at work. We were going over all the daily academics of talking about letters and the sounds they make, sign language for different words, and naming colors. I started to wonder what all this meant. What if a kid stopped me in the middle of a lesson and asked, "What is color?"

I talk about it all the time. I "teach" by pointing to an object like a banana, for instance and say, "that is yellow," but does that really explain what a color is? It seems like such an example falls short of the plethora of meanings behind color.

I know that color can be used as a noun or verb. We talk about the color of things and to color things as an action such as coloring a picture or using color to reflect emotions, etc. But what I want to know is, when we look at something that is red, what are we actually seeing and how do we know its red?

The dictionary's first definition of color is: the quality of an object or substance with respect to light reflected by the object, usually determined visually by measurement of hue, saturation, and brightness of the reflected light; saturation or chroma; hue.

Okay, so its all about how we perceive the light that is reflected off of a given object. What about people that are "color blind?" They see color differently. How can someone say that they are blind to what is "normal" color? Maybe it goes both ways. Since the majority of people are blind to what color blind people see does that mean we're all blind? Blindness indicates a deficiency and is hardly a good way to describe differences in perception.

Even between two people who are deemed to not be color blind, a color could possibly be perceived in very different ways. Especially when the subject comes about in a special ed classroom like the one I work in. There are many degrees of vision in each child and we really can't be sure what they're seeing because most of them are nonverbal.

How can I say that I really know what color things are when there are so many perceptions all around me? Who is right? Am I right to say that a banana is yellow when a kid might look at it and actually see purple? Maybe there's a whole different or additional spectrum of colors that most of us have never experienced that's available to these kids.

Who's to say? Once again I'm baffled at how little I really know. I guess I'll have to keep doing it the way I know how and just pay attention to the reactions I get from students. Most importantly, I should shift my focus of awareness from how I can teach them to what I can learn from them in an attempt to further understand each subject.