Color matters. Size matters. Some days not so much, other days VERY MUCH. Rob, I agree that SUBTLE changes don't make any difference, however, large variations on a theme often do.
Not fishing through a run more than once? Huge mistake if you happen to be fishing a fishery whereby you are pursueing MOVING fish. Your observations on the Washougal may indeed hold true for that particular river and similar rivers within the area, but that does not mean that they are applicable to all rivers or races of steelhead.
Back to the color theme. All Pacific salmon, including steelhead, display fairly similar life history traits. I don't think that it is too farfetched to say that they also all have similar, though not exact, behavioral traits. Ask anyone that has had just a fair amount of experience flyfishing in Alaska over HORDES of FRESH silvers, chums, or the less numerous but still significant Chinooks whether or not color makes a difference. I cannot even remember how many times fishing for chums or silvers that the color pink, regardless of the size of pattern, would outfish any other color by a margin of 10 to 1. Then on other days it would be purple. It was pretty darned obvious that in these cases that it was absolutely the COLOR that made the difference, not size of the fly, not even presentation. These experiences convinced me that color is an important aspect to consider when flyfishing for steelhead, but that that importance can vary according to the conditions.