I'm rather new to the game, but have been reading up quite a bit, and playing a large amount as well. I'm currently level 28, and trying to piece together a strong team. I have found that most leader abilities revolve around the creatures of their color, but as well am finding that it's nigh impossible to build a very strong team out of just a single color. Each color lacks something that another is able to provide.
For example, Red lacks dependable healers.
Green lacks poison (from what I've found and read so far).
Black lacks high HP cards.
The list goes on. Anyway, my question is this: Is it generally going to be better to mix colors into your team? Or to stick with a single color once you obtain the proper cards and command points? So far I've been mixing a max of two colors, trying to maintain the majority of benefits of a mono-color team, but having one or two cards of a second color to aid the main color's weakness.