What is the background colour of a skull and crossbones placard that signifies a poisonous substance hazard?

The background color of a skull and crossbones placard that signifies a poisonous substance hazard is white. This is standardized in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and aligns with the National Fire Protection Association (NFPA) and other regulatory frameworks that use a white background to indicate this specific hazard. The skull and crossbones symbol itself is universally recognized as a warning of toxicity and the potential danger posed by harmful substances. Utilizing a white background helps to ensure clarity and immediate recognition of the hazard by first responders and those who may come into contact with the substance, thus prioritizing safety and effective communication in hazardous material scenarios.