Dual Lands such as Tropical Island, Tundra, and Underground Sea
While one major downside of this commander is the requirement to access Phyrexian Dragon Engine, black is the color with the easiest access to strong tutoring effects, allowing you to more readily access this commander's melded form
Blightwing Bandit Flying, deathtouch Whenever you cast your first spell during each opponent's turn, look at the top card of that player's library, then exile it face down
Even if you're not playing a Kindred theme that will just take Radagast out of consideration entirely, you will eventually hit a happenstance of creatures in play that will have you putting creature cards on the bottom, not to mention the likelihood that you'll pull all non-creatures
You never want to choose more than three colours (at least, most of the time) and if you want to be safe then having two is probably the best way
For the Common Good is one of those cards that has helped facilitate that growth