Most guide and direction signs in Ontario have a green background, but you pass one with white lettering on a blue background naming the municipality you are entering. Is that a different category of sign?

Correct answer: C. Yes — blue is used for boundary, downtown/city centre and port or industrial area signs

Yes — blue marks a particular family of guide signs. Book 8 sets out that a specific group "should be shown with a white retroreflective message on a blue retroreflective background": the Boundary Sign, the Downtown, City Centre and Business Area Sign, the Port and Industrial Area Sign, and the "TO" Downtown from Airport Sign. So the blue ones tell you *where you are or what kind of area you are heading into*, while the green ones handle routes, destinations and distances. Blue is also used as the background for ordinary guide signs in two special settings — the collector lanes of complex freeways, and Highway 407 ETR — so a blue sign is a prompt to read it, not to assume its meaning from the colour alone.

Source: MTO Driver's Handbook: Ontario Traffic Manual, Book 8 — Guide and Information Signs, Volume 1, Section 5 — Design Commonalities, Colour