For the silvers, try hot pink or hot fuschia bunny flies with cerise and dark blue Kystal Flash tied at the front and nearly as long as the bunny strip tail on a #4 or #6 hook. Tie the bunny as a zonker at the rear of the body and then add a hot pink or fuschia plastic chenile body. tie the body off befor the hook return and then pull the bunny strip forward, tie it off and then wrap it aroung the hook 2 or 3 times. This fly can be weighted with bead chain or extra small lead eyes.
Another fly to try would be what I call a Blue and Purple Pheasant, also on a # 6 hook. It has a tag of silver oval, a purple braided mylar body, very light blue calf tail wing, and a blue-phase ring-neck phaesant rump feather collar hackle tied after the wing is tied in. This fly works well with upriver silvers.
A third choice is a flash fly again on a #4 or #6 hook, Silver Flashabou tail, silver body (I like metallic Estaz), red, blue, purple, or hot pink hackle, and a silver Flashabou wing.
Fish all of these with some movement by stripping it the line at various retrieve rates from slow to extra fast until you find the one the fish hit.
They have also picked up the bunny fly on the swing, especially the biger fish seem to like the bunny fly fished this way.