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For the preface to the Color website:
[Start with a photograph out of doors -- for example, a red-haired person in a partly sunny landscape with lightning and a rainbow].
Color "colors" our whole lives. Our sense of the world we live in comes first from what we see. What we see is colored; and the colors of our world affect us deeply. The sky is firstly blue sky, the grass green grass, a red head a red head. We value color so highly that, for thousands of years, we have tried to make our lives more colorful, by coloring our clothes, our homes and even our faces. Today, for the first time, we are able to color anything in any way we want; and that remarkable achievement is one consequence of the Industrial Revolution of the past two hundred years.
What is color and what makes some things colored and some not? How are we to describe and understand such a powerful feature of our life? Color is fairly complex. There is not one source of color but rather three different sources of color. Color always involves three things — light (obviously), our eyes (which is how we detect the light) and the object (which we will identify as colored). The color of our object can have three different origins which we can label as absorption, emission and scattering. In our picture, the green of the grass and the blue of the jeans are due to absorption. The lightning is due to emission. And the blue of the sky and the colors of the rainbow are due to scattering. Each different type of color —absorption, emission and scattering —occurs naturally — grass, lightning and rainbows without the participation of man. Man, in making his life so much more colorful, has simply exploited these natural effects.
- In absorption, light — sunlight which is white light — strikes an object and part of the light may be absorbed by the object. The light we see coming from that object is the light which was not absorbed by the object. We see the "not-absorbed" light as the color of the object. If no light is absorbed, the object appears to be colorless. Vegetation, such as the grass in our picture, absorbs all the light except green light and that absorption, perhaps the most important process on earth, drives photosynthesis and makes life on earth possible. The paints and dyes produced by man as artificial colorants appear colored for the same reason that grass appears colored: they absorb some of the light that strikes them. The jeans in the picture show man as a color maker, in this case not a very good colormaker. Over time the jeans fade.
- In emission, the object makes colored light and "throws" it at us. It actually does no"make" light because it cannot "make" energy. We can only transform energy from one form into another. (This ia fundamental law of physics, based on experience: "Matter/energy can neither be created nor destroyed".)