What color flag must be attached when towing another vehicle with a chain?

In many jurisdictions, when towing a vehicle with a chain, a red flag must be attached to the chain as a cautionary measure. This is to ensure that other drivers are aware of the towing situation and to help prevent collisions. The flag serves as a signal that there is a non-standard road condition—a vehicle being towed—making it visible to approaching vehicles. Using a brightly colored flag, typically red, enhances visibility, particularly in low-light conditions or on busy roads, ensuring safety for both the driver towing and the one being towed.

The other colors listed do not typically represent the same cautionary message that a red flag does in the context of towing.