Colon Between Independent Clauses
A colon can be used to separate two independent clauses when a) the second clause is directly related to the first clause (not just vaguely related) and b) when the emphasis is on the second clause. While you can also use a semi-colon or a period between two independent-yet-related clauses, the colon is a little softer than the period, but a little harder than the semi-colon.
In British English, the first letter after the colon is only capitalized if it’s a proper noun or an acronym; in American English, the convention depends on the format but it’s frequently capitalized. If your writing must follow a specific format, check the rules for that format before capitalizing (if in doubt, it might be safer to use the lower case).
It’s been snowing for three days straight: The roads around here aren’t very safe for driving.
Maggie wears a brimmed cap at all times: Strong light often gives her a headache.
I’m looking for a copy of Wind in the Willows: one of my students wants to read it.
The library is very quiet tonight: I’ll get a lot of work done.
My niece is the star of the show this evening: she’s the one in the pink tutu.