What is the standard color coding for a three-phase power supply in the United States?

The standard color coding for a three-phase power supply in the United States is black, red, and blue. This color scheme is widely accepted and used in electrical installations, especially for identifying the three phases in a multi-phase system. This helps ensure consistency and safety among electricians, allowing them to quickly and accurately identify connections and inputs in industrial, commercial, and residential applications.

In the context of electrical work, adhering to standardized color codes is crucial for preventing mistakes during installation and maintenance, which could lead to dangerous situations such as short circuits or equipment damage. The other options, while they might represent different coding systems or have valid applications in specific contexts, do not reflect the recognized standard for three-phase systems in the U.S.