hank,
I suppose it depends upon what theories we are discussing -- I have millions of them.
If you mean the matters on light and filtering that I posted above, those are not theories, but simple facts of optics. I employ such principles in designing the UV bandpass camera filters that I sell to photographers, scientists, astronomers, etc. around the world. I also use these principles in designing and reformulating the UV camouflage (patented) for military use. No brag, just detailing application of knowledge.
Now, if you mean applying those principles to the flies and where do I test them, that is a different matter. Here in NH, the Granite State, our streams tend to be rocky, high-gradient, freestone streams. Very clear water, generally. Unfortunately, the bog ponds, and the streams flowing from them which would be colored, are inaccessible to me now. Heck, it can take me thirty minutes just to get sixty feet from my favorite pool to the trail.
So, my days of chasing little streams up into the hills are, alas, gone.
I hope I answered your question.
Regards,
Reed