Krill and sandshrimp make up a huge part of a steelhead's diet. Start there. For some reason steelhead hate crawfish, with a passion. They pick them up in thier mouths and kill them. Thats a great 3rd choice. I love anise oil, but I wont waste that stuff on yarn balls. It only goes on my eggs.
As far as color's go, it depends on the water. If its high and dirty, reds/pinks/and orange's. If its in the middle, Different shade's of pink. Light pink with a darker pink is money. Low water I love bubble gum pink and white or pearl pink.
I would say 85% of the time im running my yarn balls with eggs tho, Thats where my scent comes from. And my eggs can all have different scents to them. But those 3 are the top 3.