Let me say for the record that I'm not a big fan of Gary Borger's contributions to our favorite pastime. I believe he is a "turbidifier", not a clarifier. Having said that, I still think a system of color definitions would be useful, such that a subjective text description (e.g. "medium brownish olive") could be more accurately defined. (In addition to, not instead of, the text words)
I've convinced myself over time that, of the things that matter in fly imitation (presentation, size, profile, color), color is the LEAST important. Nevertheless, I've had times when color definitely mattered. Solving the puzzle is never easy, and color can figure into the equation.
John, good to see that the Flick
Streamside Guide cortical implant is still functioning. You are of course correct. Roy Steenrod, who first tied the Hendrickson, never wrote a book, but he is quoted by several author/historians as describing the body as "fawn colored fur from the belly of a red fox". I guess Steenrod didn't think the sex of the fox was important. Were Flick's trout more selective? I doubt it.
Fawn colored? Urine burns? Those are all rather vague terms. The Hendricksons I see in Wisconsin (I wish I saw more!) most often look about this color (a page from my BCS booklet):

The male Hendrickson (a Red Quill) is elsewhere in the booklet.
This thread has gotten pretty geeky. Sorry Mike. --Phil