The use of red on signs is limited to stop, yield, and prohibition signs.
A white background indicates a regulatory sign;
yellow conveys a general warning message;
green shows permitted traffic movements or directional guidance;
fluorescent yellow/green indicates pedestrian crossings and school zones;
orange is used for warning and guidance in roadway work zones;
coral is used for incident management signs;
blue indicates road user services, tourist information, and evacuation routes;
and brown is for guidance to sites of public recreation or cultural interest.
Anything from upcoming ammenities to what radio station you should tune to for information during evacuations (hurricane evacuation routes have these regularly)