There are eight shapes and eight colors of traffic signs. Each shape and each color has an exact meaning, so you must acquaint yourself with all of them.
GREEN: Guide, directional information.
RED: Stop, do not enter or wrong way.
BLUE: Motorist services guidance. Also used to identify parking spaces for disabled drivers.
ORANGE: Construction and maintenance warning.
BROWN: Public recreation areas and scenic guidance.
YELLOW: General warning.
The shape of a road sign can tell you as much about the sign's message as its color.
Octagon: Exclusively for stop signs.
Horizontal Rectangle: Generally for guide signs.
Triangle: Exclusively for yield signs.
Pennant: Advance warning of no passing zones.
Diamond: Exclusively to warn of existing or possible hazards on roadways or adjacent areas.
Vertical Rectangle: Generally for regulatory signs.
Pentagon: School advance and school crossing signs.
Round: Railroad advance warning signs.
Crossbuck: Railroad crossing.