So, first, I'll give an overview of the five Colours of Magic. Magic [Def. #2 [http://dictionary.reference.com/browse/Magic]] in Magic [TCG] isn't all the same. There are different kinds. And while different kinds of magic can produce the same effect, they usually won't do so in the same way, or with the same amount of energy/mana. The five Colours are: White, Blue, Black, Red and Green. Each colour has two enemy colours, and two allied colours. If you take a standard pentagram, and put White at the top, then the rest in the order above going clockwise, you have the allies and enemies - the allied colours are adjacent, and each colour's two opposites are the enemies. So Blue is allied with White and Black, and opposes Red and Green. Pretty simple, so far. But what does "Blue" mean? It's got a capital 'B', so it's probably not that it's got an azure hue. So here goes:
White - White is characterised by a desire for peace and security and stability on a large scale. White guys look out for each other, and will very often make use of laws or rules as ways of keeping the peace. People who tend to be white are cops, and politicians. White characters aren't just looking out for themselves, though, or even just other White guys. They're looking out for the whole world. And White does this by creating structure. Laws and rules which apply to everyone will result in a harmonious world for everyone. That's what White says. So White has two sides - benevolence to those who would follow its laws, and wrath towards those who would break them.
Blue - Blue people are opportunists. To our Blue person, life's purpose is to learn what you should be, and to learn how to be that. So in order to find out where Blue should fit, Blue seeks knowledge and information above all else. So Blue's long-term goal is omniscience: The ability to know the place of everyone and every thing. Blue characters tend to be thoughtful and considered. Blue will always think of a plan before rushing in, and will always seek to maximise the knowledge gained. Potentially Blue people are students and scientists, who seek to understand the world by learning and by experiments. Note that Blue characters will almost never destroy anything - they'd much rather steal it or otherwise control it. Because if it's destroyed, it's gone, and it's not coming back. If it's mine... well, then it fits where it should be.
Black - Black people are selfish. That's the simplest way to describe them - Black is the colour of the Self. Every single thing a Black character does is only to benefit himself. Working with a team? Because I can gain strength I wouldn't normally be able to. Saving someone? That someone might know something I can use, and if they don't, well, I'm sure they have gold on them. Black's final goal is omnipotence - the ability to do whatever the hell he likes. And if someone's in Black's way, well, he'll find a way around them. Black won't hold back: He'll use every single tool, every single power available to him to get what he wants. Black isn't limited like anyone else, Black is sheer ruthlessness. Black people are villains: Thugs or criminals are very often Black, and ambitious politicians or businessmen can also fall into this category.
Red - Red guys are fuelled by emotions. People fuelled by anger and rage get the most press as being Red, but people fuelled by Love or despair are just as Red. Red comes from the heart, not the head. Life's pretty simple for Red - do whatever you want at the time. Forget this long-term planning stuff, that's a waste of time. It's all about what you want to do right now. So do it! So Red people hate rules and laws and stuff like that, because it limits what they can do. Which sounds a lot like Black, but isn't as similar as you'd think - Black ignores laws because they're in Black's way, Red ignores laws because they limit freedom. Red is aaaall about freedom as an ideal. And if other people are constrained by laws, well, those laws have got to go. Which tends to mean that so do the people enforcing them. It's very hard for a Red person to live in a traditional civilisation, which tends to be White. Guys who might be red are your bullies and thugs, but also your artists and great lovers. It's all about having fun, for Red. Though, if that means smashing someone's face into the dirt, so be it. Not because I hate that person, or because that person has something I want, I just feel like it.
Green - Green is Nautral. Green is the Colour that most animals/monsters/etc in their natural habitats would get. Mr Green values the natural order over everything else. He would like nothing more than to let the world run its course, without any interference from anyone or anything. Greenie loves to see things grow, and take their natural shape. Green things are wild animals, and nature-deifying tribal types. Additionally, parents all have a Green streak to them, because as much fun as it is to shape your child into your image, most people are very very happy to let their child grow into whatever they want to grow into. And since Green is in favour of defending the natural order, they tend to be in favour of defending everyone who thinks similarly. But what really ticks off Mr Green is when people start getting these ideas to interfere with the natural order, and start imposing their own ways. When people start to shape things. Gardeners who create topiaries are NOT Green, they're more likely to be White. So Green gets angry. And Green smashes. Interestingly, the Hulk is Red, not Green, and Dr Banner is Blue.
If you read that, and are going "The hell?! That wasn't brief!", well, yeah, it kinda was. If you want to challenge me on that, I'll link you to an in-depth discussion on each colour.