I'm sure the answer varies widely depending on fishing conditions -- species, still or moving water, season, etc. However for stream trout here in the driftless area of the midwest, I'd go with an orange colored scud. I fish scuds in our spring creeks from January through September (our entire season). I have several orange color variations -- some brighter with some pink, some with more yellow for an overall amber color, and some tannish and more subdued. I change the trailer fly fished behind the scud to match seasonal hatches -- eg, Baetis nymphs right now -- but throughout the season a scud is my lead fly way more often than not. I'm quite sure that I've caught fish on a scud in every month this year and maybe even every week.