Clients often have trouble seeing their white-posted flies in heavy foam or under midday glare. Since seeing your fly is critical to successful fly-fishing, I've been experimenting with several new post colours that stand out under those conditions.
Guides occasionally lapse into thinking that it doesn't matter if clients see their flies - that the guide will yell "set" or "now" when it's time to strike. But that's just laziness - laziness on the oars and laziness at the vise. It matters if clients see their flies because: 1. it adds to the fishing experience; and 2. it puts more fish in the net.
Last year on Michel Creek my clients were casting dries to large cutthroats rising to Green Drakes along a thick foam line. The sky had that washed-out haze so common on August afternoons. They were having trouble seeing their flies, despite the flies' relatively large sizes, and so was I. On a whim, I tied on a #12 drake pattern with a bright blue post. The effect was immediate: it showed up really well, and the trout seemed to like it, too, taking it again and again until the fly unravelled and the gig was up.
You see, it was the only one of its kind in my box. The clients rightly chided me about only carrying one fly of a specific pattern (a strict guiding no-no), and I learned my lesson. But I also learned that in future I was going to be a lot more creative with my choice of post colour beyond the traditional white, pink, and chartreuse.
Don't get me wrong; white and chartreuse still have their places, and a fluorescent pink- or red post is tough to beat at sunset, when the natural light is teeming with that end of the spectrum. It's just that with the multitude of colours available to fly-tyers nowadays, you can pretty much tie a post to match any light or water condition.
I sometimes combine several 'unconventional' colours on the same parachute post - a 'bivisible' variation. Ocean blue/white is great under alternating sun and cloud, while black/fluorescent orange excels during and after sunset, when harsh glare gives way to soft pastels gives way to silvery monotones: nothing shows up like black silhouetted against the silver sheen of a river's surface after sunset. Don't believe me? Try it some time and be convinced.