"She has absolutely gorgeous blue eyes." "How green the leaves are." "The piano keys are white. 'Even in the shadows?'." Yeah, than, what "color" is the "clear" glass, or the water in the lake, or the reflection of your face in the brass door ornament or in the china plate on the dining room table? It's always the color of the object that is talked about, but what does that mean?
Have you ever noticed that when you turn out the lights everything turns black (duh!) Even the white painted walls, can you really call them "white" now? Have you ever been to a play or musical and watched as the spotlight shined on the lead actor and he, all of a sudden, turned blue, or green, or red? What is going on here? Have they really changed color, or is it that their color is really something that doesn't belong to them but to some other entity and can strangely be changed at will?
Well, it's kind of both. You see, the color of an object comes both from the light that falls on it and to some properties of the object itself. If you get down close to the object, I mean really close, like down to the molecular level, the shape or texture of the surface is one of the things that control what kind of light is reflected or "scattered" off of it. No surface is really "perfectly" smooth, not in this universe. Objects' surfaces are made up of little bumps, and these bumps are pretty much regular or even which makes them like a tuner on a radio or television set. On an even finer level the bumps are the atoms themselves, and the clouds of electrons that belong to them (you remember electrons, don't you? Those things that "orbit" the nucleus or centers of atoms, right?) Well, they have a lot to do with what color an object appears to be and how much of it is reflected. Light waves are a strange phenomenon in that they act very peculiar down at the very tiny sizes and distances of the bumps that make the surfaces of things. Light also acts like little balls when it wants to. We call them "photons", and they usually "bounce" off of the objects that they strike, like a handball off of the court wall. What color these photons represent depends on how energetic their bounce is, how "lively" they are or the amount of energy they were born with, and how much of that energy they've kept on their journey to the object they encountered and how much they bounced off with.
The color of something is also related to the frequency or wavelength of the light reflecting off of it, like the difference between the short distance and frequent lapping on the shore of the ripples on a pond and the large span and long time between the crashing of the waves on a beach. In some cases objects make their own light, like light bulbs and stars. We say they are luminous. We use them as sources of light and the qualities of the light from them will be a factor in the light that is reflected from what they illuminate. This is where we can consider the photon's energy as being the source of the color. Hold a piece of "white" paper under a red light, it looks red. Hold the same piece of paper under a blue light and now it's blue. This is neat because it is one of the ways the director of a movie or a play can generate "mood" on stage or film.
Things that emit red light are cooler than things that emit blue light. Really, red light has much less energy than blue light. This might be hard to accept when you think of a "red hot" coal or fireplace poker, but remember that it's always the "ultra-violet" light that you are warned about, invisible light that is off of the blue side of the rainbow, that gives you a sunburn. If you want to argue that red-hot coals will burn you, consider this: you can sit in front of the red campfire embers all night for comfort and companionship and not get a sunburn. The real reason that you get burned from touching a red hot coal is because the energy emitted from it is mostly not light but heat energy which, for the most part is invisible, and as you get closer to the coal it is madly moving air molecules that you feel as the heat until the time when you actually touch the coal and the molecules are vibrating so violently that it's like rubbing your skin very hard and quick and fast, and that's what burns you. Light, on the other hand, gets more energetic as it goes from the "darker" red side of the spectrum to the "brighter" blue side. It takes much more energy to produce blue light than red. Knowledge of this property of light is how astronomers were first able to tell the temperature of individual stars.
Here's something you can try: Find a piece of metal, a brass name plate, a copper pot, a chromed picture frame. Here are three metals that have different "colors". If they are old and dingy the experiment would be even more exciting (get some metal polish and a good polishing cloth, though!) Without doing anything to the surfaces take them into a room with an incandescent lamp, that's the kind with the "yellowish" light, the round, screw-in type light bulb, and put the objects under the lamp and turn on the light. Look at them carefully and try to remember the color. Better yet, if you can, take some color pencils or crayons or other coloring media, and try to imitate the colors of the items, but don't hold your pad under the light, do it out of the direct influence of the bulb. Now do the same under a fluorescent light. In my time kitchens were always the best place to find one, they are usually in the shape of a long glass tube, or in kitchens, a circular tube. Their light is very much white although companies do manufacture what are considered "natural" light and other fluorescent bulbs. Is the color of the objects different now that they are lit up under this bulb? Use your pad to try to mimic the colors again, remembering not to be directly under the light, and do this on the same sheet of paper. Take the objects outside. Different conditions will present different lighting conditions, sunny sky, cloudy sky, at night, go under a street lamp with them, maybe a different street lamp (ever notice some are "white" and some are "pinkish"? Why?) Repeat the experiment.
Now, if you happened to get dingy or tarnished objects and have the polishing tools suggested above, shine 'em up! Do the experiments again and see how different they all are! Did you happen to take them into a back room or a closet where there isn't any light? What was your conclusion about their color there? "I couldn't see them! I need some light!", you might have thought. Of course you needed light, and so in the dark they seem to have no color! What does all this mean? Take some things that aren't shiny and do the experiment with them. Look through running or standing water or look in a mirror and see if you can describe it's color. Why is green glass green?
I, with my scientist hat on, would say that the "visual color property" of the objects changes as the conditions change. It depends on the material the object is made of, what it's surface is like, how close and regularly spaced the "bumps" are, and some more things about the atoms that make up the material of the object. It also depends on what kind of light an object is under, or whether there is any light shining on the object at all, as to whether the thing has a color and what you might say that color is. In the dark I would say that the visual color property is null (unless we're talking about a luminous object), meaning that the things about it that cause it to have a color haven't changed except because color is really light, and the light that strikes your eyes is how you perceive it's color, since there's no light it's color has ceased to exist, and that has made it senseless to talk about it because when people talk about an object's color they are usually referring to the color it appears to be, the frequency or the energy of the light reflected by it.
The recording of the "colors" of an object and the conditions under which these colors are noted should be considered an important item in the observation of the object. A good scientific description should always include the basic quality of color.
This page was last updated 02/10/03 EST