Q. I cannot find anything in CMOS to corroborate my hunch that a capital should be used in cases like the following: (1) “Please note: It is important to unplug the appliance after using it.” (2) “Hint: You may not need all the letters to solve the puzzle.” (3) In the acknowledgments section of a book, “Jennifer, James, and Joe: Thank you for all your support.” Some might argue that the word following the colon in each of those instances should begin lowercase, but that doesn’t seem right to me. Thanks for your help.
A. We agree with your hunch. When a word, a phrase, or a dependent clause introduces a complete sentence with the help of a colon, that sentence usually gets a capital letter:
Note: Semicolons are not allowed past this point.
and
Please note: Semicolons are not allowed past this point.
This is exactly how speech tags work (and see CMOS 6.69):
She said, “Find your own way.”
or
She said: “Find your own way.”
And though CMOS used to advise capitalizing the first word following a colon only when it introduced more than once full sentence, we now advise an initial cap for any full sentence introduced by a colon:
The end of the party was signaled by an abrupt silence: The generator had run out of gas.
but
The end of the party was signaled by an abrupt silence: no more gas.
See CMOS 6.67.