Introductory phrase preceding colon
When a colon introduces a list, the text that precedes the colon must be able to stand alone as a complete sentence.
Not recommended: The fields are:
Recommended: The fields are defined as follows:
Bold text preceding colon
When the text preceding a colon is bold, make the colon bold too.
Colons within sentences
In general, the first word in the text that follows a colon should be in lowercase.
Recommended: Tone: concise, conversational, friendly, respectful.
Recommended: When you add or update content to an existing project, remember to take these steps: review the style guide; use checklists; enlist a fellow writer or an editor to copyedit your work; and request a developmental edit if you feel that it's warranted.
For information about when it's better to use colons than dashes, see Dashes.