What color and shape typically identify warning signs?

Warning signs are indicated by a yellow diamond shape. This distinctive color and shape help drivers quickly identify potential hazards or changes in road conditions ahead. The use of yellow as a background color provides high visibility and alerts drivers to take caution. The diamond shape is specifically designed to stand out from other signs, making it easier for drivers to recognize warnings, such as sharp turns, intersections, or pedestrian crossings.

The other options do not accurately represent the standard for warning signs. For example, black circular signs generally indicate regulatory information, while white rectangular signs usually provide information or directions. Green square signs often indicate guide information, such as directional signs. Therefore, the yellow diamond is specifically designated for warning signs, making it the correct choice.