THE PROBLEM WITH COLOR
If you have ever tried your hand at artistic painting you are aware that color is a complex subject. There are large thick books that drone on and on about color theory, and college level classes that delve, with great detail, into the intricacies of color. You learn that color can be transparent, translucent, opaque, reflective and refractive. It's affected by the intensity and direction of light, and even the angle of the viewer affect the appearance of color.
Color has three properties: hue, value and Chroma. Hue is that property by which we distinguish one color from another. Value is that property by which we distinguish darkness from lightness of any hue. Chroma is the property by which we distinguish brightness or dullness of any hue; and is often confused with value. So, we have the basic hue [color] which has a value [lite or dark] and Chroma [bright or dull] and each one affects the way we perceive color.
What does all this have to do with fly fishing? If you're a person that believes that your fly has to be just the right color it means everything. If you're a generalist that believes size, shape and presentation are more important than color then it means very little to you. If, like myself, you find yourself somewhere in the middle color theory, as it pertains to artificial flies, is an interesting side note.
If you are a fly angler that fishes predominately for salmonoids, trout, steelhead, salmon, then you're aware that the hatches and the flies used to imitate them are closely tied to color. We have blue-winged olives, gray, yellow, brown and green drakes, tan, black, gray and green caddis, yellow sallies, and midges in nearly every color in the rainbow. To complicate the matter even further we have shades [values] of these colors - lite, medium and dark shades [values] of each of the colors that we perceive and combinations; for example: yellowish-olive.
In 1924 J.W. Dunne published a book entitled Sunshine And The Dry Fly. His work was largely ignored and most anglers have never heard of him or his book, but he was fascinated by translucency and tied his flies with colored silks. What he discovered was that, when the fly was 'oiled' or treated with floatant, the body turned black. When he unwrapped the silk he discovered that it was still the same color but it had become transparent and the black color that he was seeing was the color of the hook shank. To overcome this problem he started painting his hook shanks white. Dunne's ideas were interesting but the problem with his solution involved a certain characteristic of color. When the flies were in bright sunlight they were one color but when the fly was fished in the shade or on a cloudy day they lost their translucent qualities.
This is the same problem modern anglers have to deal with when attempting to precisely imitate the color of natural insects. The realities of light and color all conspire to frustrate their best attempts. This is easily illustrated by a couple simple actions that any angler can perform.
First, take a fly out of your fly box, preferably a fly with a distinctly colored body like a Cahill pattern. Put the fly in the palm of your hand and look at this fly in the sunlight. Unless you have trouble identifying colors it should appear yellow. Now, hold the fly up to the sun and look at it from below. Does it still appear to be as yellow as it did when it was in the palm of your hand? Next, put the fly in the palm of your hand and shade the fly with your other hand. What are the results? Take the fly into a dark room and hold the fly up against a dim light source. I will wager that the fly looks black. These simple experiments will give you an idea about the problems with attempting to imitate the color of natural insects as they appear to the fish. In addition, we do not know how fish perceive color which further complicates the problem.
The question of color is another one of those topics that will be discussed around campfires among fly fishers for the next one hundred years without a real solution. Like so many of the questions that fly fishing raises. I think it best to accept what we can't truly understand and enjoy the challenge that it presents.