Regulatory signs are primarily red and white, indicating necessary actions for drivers. Each color combination listed corresponds to different types of traffic signs. Therefore, the correct choice does not include the alternatives provided in the question. ;
Regulatory signs are primarily red and white, indicating necessary actions for drivers. Other color combinations like orange and black, yellow and black, green and black, and white and black serve different purposes in traffic signage. Therefore, the correct choice is that regulatory signs are red and white.
;