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First off, if you're writing for the government they might have a format they expect, so if so and it says something on this point, it wins. Otherwise, I would not use colons in any of your titles...
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/5456 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
First off, if you're writing for the government they might have a format they expect, so if so and it says something on this point, it wins. Otherwise, I would not use colons in any of your titles or paragraphs. The colon's job is to introduce what follows (e.g. in a list), but a title/subtitle/subsubtitle/etc structure already provides that implicitly. The one case where I would use a colon in a title is in a document title that has a subtitle, e.g. "A History of the McGuffin: A Literature Survey". But I would prefer to represent all of that as the title, not title + subtitle, so I would only do that if a style guide forced me to separate the elements.