Something a lot of people don’t realize about colons is that the text preceding a colon must stand as a complete independent clause (it must constitute a grammatically complete sentence).
Let’s look at these two examples.
The following are some Netflix shows we watched last year: Squid Game, Cowboy Bebop, and Hellbound.
This text before the colon is a complete sentence, so the colon is justified here.
Here’s an example of how NOT to use a colon.
We watched lots of Netflix shows last year including: Squid Game, Cowboy Bebop, and Hellbound.
If the text ended where the colon is placed, it would not be a complete sentence, so the colon is incorrect here. To make this sentence correct, simply remove the colon. No punctuation is needed.
Hopefully this helps everyone make fewer mistakes when using colons. I plan on posting another rule regarding colons tomorrow.