Major Archetypes:
W/U or W/B: RAF. White has a ton of solid flyers, and blue and black each have some. Royal Air Force with blue will probably do more heroic shenanigans, while black will make a more controlling build with some removal and possible intimidate as well as flying thanks to Cavern Lampad
G/U or G/R: Monster Mash. Green has both the best large creatures on the best ways to capitalize on them (
Time to Feed for the win). Red has better Monsters than blue does, but blue has more monsters and psuedo-monsters at lower rarities. White could theoretically work for a Monster Mash plan, but only if you're using it for pure support less Fleecemane Lion and/Or Hundred-Handed One. Green red gives better ramping from Satyrs, while blue gets
Agent of Horizons and the super-bomby
Prophet of KruphixB/G: Resource Grind. Black and green have little deathtouch creatures, including deathtouch bestow. Black has March of the Returned and B/G has Phakira's Mender. Between the two colors, you also have good removal access with Time to Feed, Sip of Hemlock, Phakira's Cure, and so on. It relies on a couple cards (particularly March and Mender) but if you can pick them up you can win just about any war of attrition. Biggest weakness is going to be the air.
Two of: W/G/U: Voltron Enchantments. Blue and Green have the best targets for a Voltron. White and Green have the best enchantments. So, this will usually be G/X, but White/Blue could work if you get
Battlewise Hoplites. the keys to this are going to be creatures with big rear ends or Heroic for counters, Ordeals, and bestow.
Benthic Giant is an all-star being a hexproof fatty, but so is
Wingsteed RiderR/X Fast Aggro: Some of the tenor of this depends on the second color, but red provides both fast, aggressive creatures and early disruption (burn) to sort it out. Red/Green will want to ramp more into bigger threats but stil llay them quick. Black has extra disruption (Phakira's Cure) and can go minotaur tribal. White adds the possibility of a late-pick Chained to the Rocks, white's typical low-end suite, and white's typical high end removal. Blue brings very little to the table, but
Voyage's End is nice and while Blue isn;t as good as white or black at it, it does has some evasive critters to give you reach.