No, not those kinds of colons. These ones
On the outset they look a whole lot more boring, but these colons are like foreplay: anticipation for what's next. They tell us something (exciting) is coming: something that relates to the previous sentence.
Colons come only after a complete sentence.
The wall of the colon allows: distention and elongation. (WRONG, no colon necessary)
The wall of the colon forms a series of pouches: they permit distention and elongation. (RIGHT)
Even in a list, make sure the clause before it is a complete sentence: so the colon couldn't come after a verb or after a preposition.
The order of the colon is: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. (WRONG, no colon necessary)
There are four regions of the colon: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. (RIGHT)
Quick and Dirty Tip from Grammar Girl:
"If you can replace a colon with the word namely, then the colon is the right choice."
For the comma portion of today:
For more on commas, see my CP Kathryn Purdie's post: Commas and Clauses.
If I got anything wrong, feel free to correct me in the comments. Can you guess what part of grammar I'll focus on tomorrow? Are you doing the A to Z challenge? Let me know and I'll come check it out.