What color finish should a screw have if it serves as the only bonding jumper?

The correct finish for a screw that serves as the only bonding jumper is green. The use of a green color is standardized in electrical wiring to indicate grounding or bonding conductors, which are critical for safety. A bonding jumper's primary purpose is to ensure that different conductive parts are electrically connected, thereby reducing the risk of electric shock by maintaining a path for fault current and ensuring that all parts of an electrical system are at the same potential.

This green finish serves as a visual indicator to electricians and inspectors, highlighting that the specific component plays a crucial role in grounding systems. Other colors, while important in various contexts, do not represent the same safety implications that green does and could lead to confusion or misapplication if used for bonding jumpers.