The following rule regarding colons occasionally appears on the SAT (please see the sublink under Literary Tools>Punctuation>Colons for additional rules):
To separate an explanation, rule, or example from a preceding independent clause.Examples:
After a sleepless night, the senator made her decision: she would not seek re-election.
Music is more than a mechanical arrangement of sounds: it is an expression of deep feeling and ethical values.
A way to remember which direction to move the hands of the clock when changing to or from Daylight Savings Time: spring forward, fall back.
The supervisor's remark was straight to the point: I won't tolerate workers who show up late.
Religion and politics can be sensitive subjects: many people hold opinionated views and are easily offended by other peoples' remarks.
There is a vital issue every chef has to consider : Will the soufflé rise properly or dramatically collapse in front of the guests ?
I will always remember the first time my husband cooked for me : It was a charming Friday Evening with a romantic candle light dinner he prepared.
Life is a series of rude awakenings: It is what happens to you while you are making other plans.