You're used to green guide signs giving route and destination information. On Highway 407 ETR and in the collector lanes of some freeways, you instead see a blue guide sign with white lettering giving the same kind of information. Why the different colour?

Correct answer: D. Blue is specifically reserved for collector-lane and 407 ETR roadway identification signs, distinct from the standard green used elsewhere

The manual specifically reserves blue retroreflective backgrounds with white lettering for Roadway Identification Signs in freeway collector lanes, on Highway 407 ETR, and on some municipal boundary signs — everywhere else, green is the standard guide-sign colour. It's a deliberate colour distinction, not an inconsistency, that helps a driver quickly recognize which set of lanes a sign applies to.

Source: MTO Driver's Handbook: Book 8, Section 2.4, Technical Considerations — Colours