Regular Expression Pattern to Match Words in All Caps That Are Followed By a colon

You want to match one or more capital letter which means you need to use a +. Also your : doesn't need to be in a character class:

[A-Z]+:

Just add a "quantifier":

/[A-Z]+:/

Note you don't need a character class for a single character.

How about \b[A-Z]+:? The \b is for checking a word boundary btw.