Colons are used:



1) To extend a sentence to expand on something previously mentioned in the sentence (e.g., I'm looking for just one personal trait: discipline.)

Think of a colon (:) as the language version of an equals sign (=) in mathematics. The information on the left of the colon equals the information on the right.

He blamed his divorce on one thing: beer.
(one thing = beer)

2) After an introduction (e.g., I've seen the following: ants, a cockroach, and a rat. )

A colon can be used after an introduction. The wording to the left of the colon will introduce whatever follows on the right. For example:

Visit: www.grammar-monster.com.

3) In references, times, and titles (e.g., Read Genesis 1:1 before 07:30. )

07:30 – Breakfast
08:30 – Meet at the lake and prepare the kayaks
09:00 – Select teams

4)With quotations (e.g., He said: "Curiosity killed the cat, but for a while I was a suspect.")

It's hard to disagree with Frank Zappa, who said: "Art is making something out of nothing and selling it."

Read more at http://www.grammar-monster.com/punctuation/using_colons.htm#Rs7j5vp08PqqxoYe.99