Q. CMOS says that you’re supposed to capitalize after the colon when the colon introduces (1) a quotation or (2) multiple sentences. But when sentences follow the colon how do you know if they’re sequential enough to warrant the capital? It’s usually really hard to tell.
A. You have to use your judgment. I’m sorry if that’s not very helpful, but rules can’t cover every instance. Don’t waste time overthinking: if it’s that hard to determine, it probably doesn’t matter.