The Rainbow Warrior was developed by competitive fly fisherman Lance Egan from Utah. I don't have a lot of experience fishing this pattern but trust that if Lance finds it effective, it most definitely is. The guy's competitive record is simply staggering.
Rainbow Warriors look really nice on curved-shank emerger hooks like the Dai-Riki #125 and can be fished in sizes from a 12 all the way down to a 22. Here I'm using a 16.
Start by mashing the barb on the hook. Oftentimes you need to do this to get the bead around the hook bend. Although this pattern can be tied with a pearl glass bead, most anglers seem to prefer it with a silver tungsten bead. A 3/32" goes well with a size 16 hook. Place the bead onto the hook, small hole first and secure the hook in your tying vise.
Red is the most common color of thread used on a Rainbow Warrior. Here, 70 Denier Ultra thread. Start your thread on the hook shank immediately behind the bead and snap or snip the tag end off close. Continue taking wraps down to about the hook point.
Natural colored pheasant tail fibers are used to form the tail of the fly. While keeping the tips aligned, strip or snip a half dozen or so fibers free from the stem. Measure the fibers to form a tail about a hook gap in length. With a pinch wrap, secure the fibers to the top of the hook shank and take wraps rearward well down into the bend. Then, wrap your tying thread forward up to the bead and break or cut the excess pheasant tail off close.
For the mylar abdomen and wing case, I like the wide version of pearl Flashabou better than the thin. Snip a single strand free from the hank and then snip a 3 or 4 inch piece from the strand for easier handling. Tie in the mylar just behind the bead and take adjacent wraps all the way back to the base of the tail then wrap your thread forward to form a completely red underbody.
Make overlapping spiral wraps with the mylar up the hook shank to behind the bead and secure it with a few tight wraps of tying thread. Pull the mylar back and take wraps of thread rearward to the hook point, this will result in an appropriately long wing case.
For the thorax of the fly, Wapsi's Sow-Scud dubbing in tan rainbow looks great as does their plain rainbow color. Create a thin, short dubbing noodle on your thread and take wraps to form a bulbous little thorax that's about equal in size to the bead. Pull the mylar forward, over the dubbing, to form a shiny iridescent wing case and secure it behind the bead with 2 or 3 wraps of tying thread. You can then fold the mylar back and take a few more wraps of thread to really lock it in place. Snip the mylar off close but don't worry if you leave a little tag, it will blend right in with the wing case.
This fly benefits from a built up thread collar, like a hot spot. Two separate 4 or 5 turn whip finishes is usually enough to build up the collar and secure the thread. With the whip finishes complete, snip or cut your tying thread free.
I like to add a drop of head cement to the thread wraps for durability. Once it dries, you can't even see it. The lip of a styrofoam coffee cup is a great way to hold small flies while the head cement hardens.
As I said in the beginning, I haven't fished this pattern a lot but I think that's about to change.