I Thought of a good way to stray from playing mono colors recently that gets you used to mixing colors. You pick a color, then your opponent chooses a spec to remove from that color. Then your opponent chooses a different color and you choose a spec from that color as your 3rd.
I know it is not perfect but it is a fun way to venture away from playing just the mono colors as I have been.
Neat idea, and very doable with the Core Set/expansions!