silver/blue is crazy good. Especially with protecting Heroes like Job or Angel of God, and banding chains including cards like Jacob, Tribal Elder, Seraphim, Simeon (+Levi), and a few others that escape my memory at the exact moment. All I know is my brother-in-law plays angels/Genesis and he seems to be able to band 4-5 different characters in different combinations almost any time he wants. It also benefits from being able to pull out a lot of Heroes quickly with cards like Angel at Shur and Numerous as the Stars. Really, the two colors by themselves are strong, but combining the two really hits what I think are some of the best aspects of each.
For gray, Syrian Raider's Camp is the best recommendation I have for now. I have been tinkering for a while with a hand-discard deck using both gray and silver (Chamber of Angels/I Am Holy) but hand-discard by itself won't take apart a person's deck at this point, and I have a hard time recommending it when the same colors have better options.
