Capitalization in Titles of Works

Q. I understand that when a colon is used to separate a book title from a subtitle, the word following the colon should be capitalized. But what if we are dealing with a paragraph heading? Final Update: the End of the World as We Know It. Should the word following a colon be capitalized? I feel it should be lowercase, following the basic rules of capitalization following a colon.

A. The rules for headline capitalization apply not just to book titles but to all the items mentioned at CMOS 8.154, including “divisions of longer works (parts, chapters, sections).” So cap the word after the colon.