Final answer:
The basic color for 'Caution' and marking physical hazards is yellow, as specified by safety protocols like the NFPA 704 Hazard Identification System.
Step-by-step explanation:
The basic color for "Caution" and marking physical hazards is yellow. This color is easy to see in all light conditions, which is why it is frequently used for safety signs and emergency workers' uniforms. In particular, the National Fire Protection Agency (NFPA) 704 Hazard Identification System uses the yellow diamond to describe reactivity hazards, such as how readily a substance will undergo detonation or a violent chemical change. These signals are essential for maintaining safety by alerting individuals to potential risks in an immediate and visually striking manner.