What color flags or lights should be used for day signals?

Using the correct color of flags or lights for day signals is essential for clear and effective communication on the railway. The established standards dictate specific colors to be used for signaling purposes to ensure that all personnel can quickly and accurately understand the message being conveyed.

This helps to maintain safety and operational efficiency, as different colors have designated meanings; for example, yellow flags signify caution, while red flags indicate stop. By adhering to the prescribed color codes, crews can prevent misunderstandings that could lead to accidents or disruptions in service.

The other options lack adherence to the established signaling principles that enhance operational safety and clarity. For instance, stating that any visible color could be used ignores the necessity of consistent signaling that different crews and personnel rely upon. Similarly, restricting signals to only red flags or only white lights does not encompass the full range of signaling requirements that are in place for effective communication during daylight hours.