Here's the rainbow fly on a tube, you can do the same pattern on a hook minus the tube steps at the beginning.
White Saddle Hackle
White, grey, red, pink, blue, and olive icelandic sheep hair
Pearl and red Krystal Flash
6mm 3d molded eyes
Step one, for the tubes, I don't have any special tools, so I made this out of a 1.25" x .25" staple, just straightened it out as best I could, then put the 90 degree bend in just at the very end.
Here is the tube, it is 1/8" OD tubing with the rubber hosing that goes just over the end to hold the eye of the hook.
The tube is positioned over the straitened staple and secured to the vise, notice that since I don't have the fancy tools to do this right, I notch the front of the tube ever so slightly to hold it from rotating over while I'm tying.
The first thing I tie in is 4 pieces of saddle hackle to give the fly some rigidity rather than just having loose sheep hair dangling out the back
Next I tie in some white bucktail to add more stiffness to the rear of the fly, a small bunch on eash side of the tube or hook will help quite a bit.
On the bottom of the tube I tie in some white sheep hair on the top of the fly
Grey goes on bottom next
Pink on top, if you look closely there are two seperate tie ins on the pink, this just take up room on the tube so I don't have too many bare gaps on the hook, I made each one smaller rather than one large clump
Turn it over and give it another stack of grey
Back on top, we add saltwater blue
Then some white
At this point I take 4 strands of KF and put it in the middle on each side, so 4 on one side and 4 on the other
I tie in some red KF on the bottom
Then follow it up with some red sheep hair, just a touch will do.
Add the olive to the top
Then glue on some 3d molded eyes. Sometimes I'll use Doll eyes
And the finished product laid out on a paper towel after being wet.