Q. I seem to find conflicting information, and I can’t figure out the following: Is it OK or not to introduce a block quotation with an incomplete sentence (such as “The passage states”) followed by a colon? Or does the sentence have to be a complete sentence?
A. Either way is fine. In fact, “The passage states” is like a dialogue tag—but for quoted text—so it can be followed by either a comma or a colon; see CMOS 6.69 and 12.41. See also the examples at CMOS 12.9–29.