A recent post about what flies to have for a trip to the Frying Pan River reminded me of something that is easily overlooked. If you are traveling to an unfamiliar fishing destination (particularly if it is at great distance), you should do some research on the characteristics of the local insects - not just a hatch chart.
Often, insects vary quite a bit.
As an example, regarding the Frying Pan, I still have a packet of "Green Drake Dubbing" from the Taylor Creek Fly Shop in Basalt, CO (on the Frying Pan River).
I have taken a picture of it next to a packet of "Green Drake Dubbing" from Bob Jacklin's Fly Shop in West Yellowstone. Now, I realize the camera does not 100% accurately capture the color of either material, but you can clearly see a substantial difference. And, this is before the material is wet. Both are for the Western Green Drake as opposed to the Eastern Green a Drake.
I don't think insect color is the most important aspect of an imitation, but I think it does matter to an extent. That is why I always stop at a local shop and purchase a few local patterns to use as examples.