The color and shape of a traffic sign communicates important information about the sign’s message. In poor visibility conditions, such as heavy fog, you may be able to make out only the shape of a sign. As you approach a sign and while still distant, you may see the color long before you can read the message or see the symbol, giving you some advance information.
Sign colors help you know what the intention of the sign is.
Red used with white conveys stop, yield, do not, and no. Stop signs, yield signs, do not enter or wrong way signs, the circle and slash in a no turn sign, and the restrictions in a parking sign are examples.
Black used with white conveys regulatory information. Speed limit, do not pass, no turns are examples where the operation is regulated by law and the black and white sign would be found.
Yellow used with black conveys a warning. Curve ahead, stop ahead, overhead clearances, slippery when wet, are all examples. A specialized class of warning signs uses a strong yellow/green color with black to advise of school zone activities and other pedestrian activities.
Green and white, blue and white, and brown and white signs are used to provide helpful information. The green sign is used to provide destination types of information, while the blue sign is used to inform regarding motorists services. The brown sign is used to advise of historical or cultural interests that might exist in the area.
Orange & black and pink & black signs are used to advise and warn in construction (orange) and incident (pink) areas. They are used with black & white signs that convey regulation that might exist only because of the construction effort or the incident.