Which background color is required on a placard for flammable liquids?

The required background color on a placard for flammable liquids is red. This color is universally recognized in hazardous materials transportation to signify a risk associated with fire. The use of red is intended to draw attention and indicate the danger posed by flammable liquids. Red placards serve as a critical visual cue for emergency responders and others in the vicinity to identify the presence of flammable substances quickly, facilitating prompt and appropriate safety measures. The distinction of red contributes to the overall system of color coding in hazardous materials, enhancing safety in transportation and storage environments.