This here is the official thread for all things MTG related. As I am sure not all of you are familiar with the came, I will explain a few basic things.
Mana Colors:White: White is the color of law and order. Protection of the weak, and the holiness of light is the emphasis of white mana.
Blue: Blue is the color of knowledge. Blue mages seek to learn whatever they can. Thought, and the manipulation of others through illusions are some of the main abilities used by blue mages.
Black: Black is the color of power and ambition. Black mages seek power through any means necessary, whether that means making deals with demonic forces, or raising legions of the undead.
Red: Red is the color of freedom. Red mages are known for their fierce passion and impulsive natures. Why waste time with an opponent's creatures when you can just burn them yourself?
Green: Green is the color of nature. Green mages revere growth, and ferocity. The revel in the conflicts of nature, and prefer the company of large beasts instead of something as trivial as books.
There are many combinations of these colors, and in general, you can make a deck that works well out of any of these color(s). Myself, I prefer to play White, Black, and Red, generally making a combination of at least two of these in a deck.