Q. My grammar books say to cap the first word of what comes after a colon if what comes after the colon is a complete sentence. I noticed you didn’t do that. (“Check it out in printed books and magazines and newspapers: you probably won’t find any double periods after abbreviations.”)
A. It’s fine to capitalize there, although Chicago style is to lowercase after a colon unless what follows consists of two or more complete sentences. Please see CMOS 6.64 for examples and exceptions.