Try this Stimulator pattern (Also in orange. olive with a darker olive thorax, and black)
Yellow will imitate Hoppers, Golden Stones ,Yellow Sallies, Caddis.
Orange; Hoppers, Salmon Fly.
Olive; Hoppers, Lime Sallies, Caddis.
Black;Hoppers (beleive it or not), Swalla stone, and Caddis.
All depending on size ,so you have to tie a lot, but believe me it's worth it