For what purpose do you use colons?

To introduce a formal business message; to separate the hour from the minutes in time notations; to join two independent clauses when they are joined by an independent marker followed by a comma; to emphasize a list; or to introduce all quotes

To introduce a formal business message; to separate the hour from the minutes in time notations; to join two independent clauses when you want to emphasize, define, amplify, or illustrate the first clause; or to introduce a list, quote, or idea directly following an independent clause

To introduce a list, quote, or idea directly following an independent clause; to introduce e$-$mail messages; to separate the hour from the minutes in time notations; or to join one independent clause and one dependent clause