permit test (sign shapes & colors)
circular signs
alert drivers of upcoming railroad crossings
orange signs
construction and maintenance warning, traffic warnings
yellow signs
general warning, road conditions or hazards, school zones/pedestrian signs, etc
green signs
guide signs, information, permitted movements/directions, highway entrances/exits
pennant-shaped signs
left-hand side of two-way zones to warn drivers not to pass other drivers on the left
brown signs
parks and recreation signs
red signs
prohibitive or stop, immediate action to avoid threats to traffic safety
rectangular signs
regulations drivers must obey, helpful info like route markers, hazardous conditions
white signs
regulations, speed limits, highway markers, no turn on red
blue signs
services, evacuation routes
equilateral signs
slow down, prepare to come to stop
five-sided signs
warn drivers they're entering an area near school, children school crossing sign
eight-sided signs
warn drivers to stop and yield
diamond-shaped signs
warn of upcoming road conditions and hazards