by Adrian Sullivan
There are a lot of theories about what to draft in Invasion. While rare cards and powerful uncommon cards can change the tone of a deck, you can expect certain color combinations to have some very distinct qualities.
Blue/White decks are usually somewhat controlling, with a large amount of evasion. While the occasional Blue/White deck can break out with Galina's Knights and fast flyers, much more common are decks that set up their defenses with Acolytes, Stormscape Apprentice, and fat blockers like Prison Barricade or Vodalian Serpents, waiting for a late game win with flyers.
White/Green is one of the less commonly drafted decks, but is occasionally popular as an anti-Black deck. Usually including the quality creatures of Green, it protects them with Acolytes and Green/White combat tricks. This deck generally has to rely much more heavily on having superior creatures and keeping them alive.
Green/Red tends to come in two flavors: Fatties or Bears. Many of these decks will fall somewhere in between the two, but it is not to hard to tell which one a player wants more: do they take the two casting cost Bears or the five casting cost Fatty? Bear decks tend to play with more combat tricks like Explosive Growth and hope to finish the game before the opponent can stabilize, whereas the Fatty decks put out fewer cards, and eventually begin to attack with their superior creatures.
Red/Black decks are of two distinct flavors. The more controlling Red/Black has overwhelming numbers of creature removal spells, and generally a few powerful threats. Of all of the color combination Red/Black is the most likely to be able to run on few creatures, though these decks generally need to have at least one extremely viable creature like Urborg Shambler. Black/Red beatdown decks, on the other hand, often have a very large number of creatures of dubious quality, such as Urborg Phantom and Viashino Grapplers. These creatures may not be able to win a fight with another creature, but the beatdown Black/Red decks will often supply just enough pressure and creature elimination that their worst creatures can do much more damage than might otherwise be expected.
Black/Blue decks are the most popular for a number of reasons. Beatdown players have the opportunity to make decks that are able to put down fast threats, and then couple it with quick elimination. Control players are able to make good use of Card Advantage with Ravenous Rats or Probe, and board control for most threats. Black/Blue and Red/Black are similar in that there is a large amount of variance between the two biggest camps, but they often share a lot of traits. The control Blue/Black deck can sometimes pretend to be a beatdown deck with the right draw, and vice versa, just like Black/Red.
When a third color is introduced to the mix, all of the above decks tend to become more controlling by necessity. Without a very consistent mana base, it can be extremely difficult to get enough pressure out of a player's hand and onto the table. The tradeoff is more powerful cards to choose from. While beatdown decks can be three colors (and often are), expect to see slightly slower decks with each additional color.
Some special mention of Five-Color Green should definitely be made. With the numerous mana helpers from green (such as Harrow or Quirion Elf), four or five color green-based decks are extremely common. While players disagree about whether or not these decks are viable, from a theoretical perspective, Five-Color Green has access to the most powerful cards that go by it on the draft table. These decks are generally much more likely to have rares and uncommons, and so are much harder to describe in general terms, but one thing is constant: they play more "bombs."
These archetypes are not hard and fast. Certainly, many more decks can be drafted by good players, but these archetypes are a good way to understand of what someone means when they say "he drafted Red/Black".