Thran lens stinks. I've seen it tried as an answer to perish, anarchy, COPs, whatever, and it's never very good. Cursed scroll and barbarian ring work great because they are overall good cards that just happen to be colorless. The fact that they can kill priests and finish the opponent off around a COP: red is just gravy. If you want something else, chimeric idol is the next best choice. It's colorless beatdown that isn't around during your opponent's oath phase. After that, maybe Urza's Rage. While it's not exactly colorless, it might as well be if your opponent just stalls the game and doesn't kill you before you get 11 mana. Even without the kicker, it's handy in a lot of situations. All of the above are good maindeck choices. SB Anarchy is a given unless you're willing to concede to white decks. The green splash idea can work in certain metagames, but it has drawbacks, too, like not always getting the green when you need it and making yourself slightly vulnerable to anti-basic land stuff (including your own Price of Progress, of which every sligh deck should run 4, divided as you choose between main and side).