Again my primary source for the information I’ll share about the use of the colon [:] is the trusty and oh-so-reliable The Chicago Manual of Style.
Besides a few specialty uses (between chapter and verse numbers in Biblical references, after the greeting in a business letter, as part of a URL) the colon serves to introduce information that illustrates or amplifies. Such may be a single element or a series of elements.
- “Tell me this as well: Jonah, who tried to escape the calling of our Lord, what was the result?”
I find this use in fiction, in dialogue, to be the exception, but it follows the principle of amplification—the question amplifies or explains what the speaker meant by “this.”
More commonly the colon precedes a list of examples or clarifying elements.
- The newspaper only covered the major team sports: football, basketball, soccer, and baseball/softball.
Please note, a colon is inappropriate when introducing a list with a verb, a preposition, or before a transition such as namely or for example.
- An author’s bio should only include information pertinent to writing, namely, writer awards, publishing credits, and writing courses.
Notice the absence of a colon after namely.
Some of my favorite books are Watership Down, Till We Have Faces, and The Book of Three.
Again note there is no colon after the verb are.
The workshop dealt with point of view, speaker attributions, and excessive use of adverbs.
In the above example, no colon is needed after the preposition with.
More often a list requiring a colon utilizes a phrase like as follows or the following.
The ingredients in this recipe for pie crust are as follows: flour, water, shortening, and salt.
In addition to the introduction of a list, the colon may be used between independent clauses, much as a semicolon is used, “though more strongly emphasizing sequence” (Chicago, 6.63).
- Many of the members of their writers’ group attend conferences: three went to Mount Hermon, and three more registered for the OC Writers’ Conference.
In the above example, the second and third clauses come naturally after the first. The order could not be reversed and still retain clarity. In other words, the sequence is vital; therefore, the colon is the better punctuation mark.
A third use of the colon is to introduce a series of related sentences.
- The agent awaited the author’s decision: Would he finish the novel first? Or would he begin his memoir while his name was still before the public?
One more. A colon may introduce speech or a short excerpt. A common use of the colon in this way is in a script. But on occasion a writer wishes to refer to quoted material and the colon is the best introduction. Here’s an example.
His favorite opening line is as stunning as it is brief: “Call me Ishmael.”
With all these uses, it’s a wonder we don’t see more colons. Their uses are perhaps more specialized than, say, the comma that appears when we want to indicate a pause.
My recommendation? Without a specific reason to employ a colon, don’t. 😀