Use a colon after a complete sentence to introduce a list
Use a colon after a complete sentence to introduce an explanation or example
Use a colon to introduce a quotation when the lead-in is a complete sentence
Use a colon between hours and minutes in time
Use a colon after the salutation in formal letters
Use a colon to separate titles and subtitles
Use a colon between chapter and verse in Bible references
Use a colon to separate ratios
Use a colon to format labels in some technical writing
Do not use a colon directly after a verb or preposition
Do not use a colon if the words after it do not complete the thought before it