Re: Small Mods = BIG differences
Oh-oh... why is it I feel the "Orange flies" thread starting??
I agree adding color and flash to subsurface flies can have an impact- it may also be of value to consider on the days one thing worked better than another, was the color of the water any different (due to turbidity or weather fouling it) and was the sky clear or overcast? These factors have a major effect on how fish see things.
As for dry flies/terrestrials, I think shape and size have more impact than color, especially in faster water or on plunge pool/pocket water type streams. When it's the middle of the day and the sky and water are both clear. color may have a bit more impact... especially in water where the trout are fished over a lot.
As I've gotten older an my eyesight isn't quite what it was, I've resorted to adding a small "pinch" of bright (or light) color CDC fibers onto dry flies either right behind the wing/hackle or as an under wing on Trudes and other down wing dries. I use Marc Pettijean's Fl Red, Fl Green, or Pale Yellow- real nice stuff an a gram goes a long way. This also allows you to use fibers from the larger feathers that you may not be able to use for other purposes.
Another trick many have used is to tie the flies one size smaller than the hook- by that I mean to tie the fly on the front 80% of the hook with a bit longer tail, leaving more of the bend exposed for greater hooking potential.
For me, the key is the silhouette of the fly much more than the color- over the past 30 years I've experimented a lot with colors and materials on flies I've had good luck with. I have one box that has 6-8 colors in 4 different sizes (12-18) of 2 pattern "styles"; the California Mosquito and Trude. The colors run the range form light gray to black, tan to brown, and include olive, peacock and at least one bright color as well.