Rules for using the Colon:
Use a colon to set off a summary or a series after a complete main clause:
Example: It is time for the baby’s birthday party: a white cake, strawberry-marshmellow ice cream, and a bottle of champagne saved from another party. (Joan Didion)
Notice that a main clause does not have to follow the colon; however, a complete main clause generally should precede it.
Colons are also used in certain conventional situations such as to separate the hour from the minute when denoting time (12:30), after a salutation in a business letter (Dear Sir:), and between the chapter and verse in biblical publications (Mark 3: 12).
