How can blue flag protection be visually identified during daytime?

Blue flag protection is a safety measure used to indicate that a train car or maintenance activity is in position and workers are present in the area, thereby requiring extra caution. The blue flag serves as a visual signal to ensure that no equipment or trains are moved while personnel are working.

During the daytime, the blue flag is used to visually communicate this need for caution. In addition, at night, a blue light is employed to maintain visibility of the warning to ensure that it is still recognized even in low-light conditions. The consistent use of blue, both in daylight and nighttime, helps reinforce the signal's meaning and keeps safety protocols clear for all personnel involved.

The other choices, while they mention various colors, do not correctly relate to the blue flag protection system, which specifically uses blue flags and blue lights for its identification and signaling methods.