The shapes used for traffic signs are the octagon, the horizontal rectangle, the triangle, the pennant, the diamond, the vertical rectangle, the pentagon, the crossbuck and the round. Colors used in traffic signs are red, blue, green, brown, orange, black, yellow and white.
The octagon is used exclusively for stop signs and the triangle is used exclusively for yield signs. The horizontal rectangle is generally used for guide signs, the pennant for advance warning of no passing zones, the vertical rectangle for regulatory signs, the pentagon for school advance and school crossing signs, the round for railroad advance warning signs and the crossbuck for railroad crossings. The diamond is exclusively used to warn motorists of existing or possible hazards on roadways or surrounding areas.
Road signs that are either black or white serve as regulatory signs. Green signs provide directional information and red signs are used for stop signs or to tell not to enter an area or that a driver is going the wrong way. Blue road signs are used for motorist services guidance and for pointing out parking areas for physically challenged drivers. Orange is used for construction and maintenance warnings and brown is used for public recreation areas and scenic guidance. Yellow road signs give general warnings.