5 Best Flies for Trout in Colorado

If Colorado trout fishing has a single defining fly, it's the midge. Tailwaters like the Frying Pan and Cheesman Canyon section of the South Platte are primarily midge fisheries - the dam-controlled, cold water creates perfect midge habitat, and trout in these rivers eat midges throughout every season. The Zebra Midge and Mercury Midge are the definitive patterns.

Sizes #22–24 are the most productive on heavily pressured water. Fish a two-midge rig under a small yarn indicator, keeping your flies tight to the bottom in the deep pools where big fish stack up. On calm mornings, look for rising fish taking midge clusters in the surface film - a #24 midge dry or cluster pattern is the answer.

Colorado's BWO hatches are among the most reliable and productive in the Rocky Mountain West. On the Colorado River and Roaring Fork, overcast fall days trigger dense emergences of Blue-Winged Olives that bring large trout to the surface for extended periods. A #18–20 Parachute BWO or sparkle dun is the tool for this moment.

Spring BWO hatches in March and April provide some of the best dry-fly fishing of the year on Colorado's tailwaters before the runoff muddies the freestone rivers. Look for hatches during the warmest part of the afternoon on overcast days - temperature and light conditions matter enormously for BWO emergence.

The RS2 - Rim's Semblance 2 - was developed specifically for Cheesman Canyon on the South Platte, and it remains the defining nymph of Colorado's technical tailwaters. Its sparse, simple profile imitates emerging BWOs and midges simultaneously, giving it remarkable versatility in the slow, clear pools where trout have time to inspect every fly.

What makes the RS2 so effective is its ability to fish in the surface film during hatches. When trout are feeding just under the surface on emerging BWOs, a #20 gray RS2 under a dry fly or fished in the film on a long leader is often the only thing that works. It's a pattern that rewards the angler willing to downsize and slow down.

While Colorado is known for specialized technical flies, the Pheasant Tail Nymph remains a workhorse on every river in the state. On the Arkansas and Roaring Fork, where a variety of mayfly nymphs are present throughout the season, the PT Nymph covers a broad spectrum of food sources with one simple pattern.

The bead-head version works well in the faster, deeper runs on the Arkansas, while an unweighted PT fished in the film during a PMD or BWO hatch on the Colorado River can be devastatingly effective. It's the subsurface fly that complements every other pattern in this list.

Summer on Colorado's freestone rivers means caddis, and the Arkansas and Roaring Fork have exceptional hatches from late May through September. On the Arkansas near Salida and Buena Vista, evening caddis emergences produce frenzied surface feeding that can last until dark - the Elk Hair Caddis in #14–16 tan is the go-to pattern for these sessions.

The Roaring Fork also has strong caddis populations, particularly in the canyon sections where fast pocket water supports dense populations. Don't overthink it - the Elk Hair Caddis is the right fly, and the presentation matters more than subtle variations in pattern.