Most of my Lake Erie steelheading was done before 1998 or so and I really don't know how the vastly amplified pressure in the intervening years has affected how the fish respond to various flies.
But, when I was fishing them, it was a pretty reliable rule of thumb that they would chase a moving fly if the water temp. was 40F or above. If it was below 40, they would not chase a moving fly, or at least very seldom.
So, in warmer water, I always fished big white wooly buggers (on a 3XL #6 hook) unless the water was very clear. Then I would drop down to an 8 or 10 and occasionally switch to black.
In colder water, I almost exclusively fished a variety of eyed egg flies. Actually, these are better called "mushroom flies" as they are just 3 hanks of glow bug yarn lashed perpendicular to the shank and then all pulled up together and clipped to a length of between 3/8 and 3/4 inch. This makes a mushroom shape that is all above the hook shank and for me at any rate, beats the h--- out of fiddle-dinking around trying to make a round egg fly.
In clear water, I'd tie these on a size 10 or so wet fly hook. If the water was dirty, I'd tie them up to a size 4. This makes a huge, highly buoyant fly that takes about 5 BB shot to sink. But it always caught fish in water where you couldn't see your toes if you were ankle deep. I never thought color mattered all that much, with the exception that I never did well on orange for the main color. I probably caught the most fish on yellow with a red eye and chartreuse with an orange eye.
I always thought that learning how the fish utilize the shale substrate of the stream when they move and hold was 10 times more important than fly choice. They'll hit anything eventually. Then they may never hit that same fly again for the balance of your natural life. I once watched my Dad hook like 7 out of one pod in 10 casts on a #8 smoke colored crappie twister jig fished on 10 pound test with a snap swivel. In clear water.
No sense often makes perfect sense when fishing for steelhead.
