As a former professional proofreader, self-proclaimed punctuation nerd, and admitted colon addict, I was delighted to stumble across Conor J. Dillon’s essay on the uses of colons in prose. The whole thing is worth quoting, but here’s a snippet:
A new colon is on the march. For now let’s call it the “jumper colon”.
For grammarians, it’s a dependent clause + colon + just about anything, incorporating any and all elements of the other four colons, yet differing crucially in that its pre-colon segment is always a dependent clause.
For everyone else: its usefulness lies in that it lifts you up and into a sentence you never thought you’d be reading by giving you a compact little nugget of information prior to the colon and leaving you on the hook for whatever comes thereafter, often rambling on until the reader has exhausted his/her theoretical lung capacity and can continue to read no longer.
See how fast that goes? The jumper colon is a paragraphical Red Bull, a rocket-launch of a punctuator, the Usain Bolt of literature. It’s punchy as hell. To believers of short first sentences–Hemingway?–it couldn’t get any better. To believers of long-winded sentences that leave you gasping and slightly confused–Faulkner?–it also couldn’t get any better. By itself this colon is neither a period nor a non-period… or rather it is a period and it is also a non-period. You choose.