Please note I am posting as a UK English writer, I point this out as I know there are differences between American and UK grammar guidelines or accepted practices. I would also add that I am asking from a novelist point of view rather than a technical writer.
Ignoring for now, introducing dialogue or lists, do I really need to worry about colons or can I use semicolons when a comma or period does not suit.
Are there any situations, within a sentence, where a colon is really the only recommended solution.
For example, in researching on the internet I came across the following example :-
A dolphin is not fish: it is a warm-blooded mammal.
It seems to me that a semicolon or comma would equally suffice. I am not asking for the correct formatting of this sentence, or for it to be corrected grammatically but rather more generally:-
Are then any such situations, with two independent clauses where a colon is an absolute must, or grammatically preferred over a semicolon, and regarded as better, writing practice.