BLUE SIGNAL 26. A blue signal -- metal blue flag by day and blue light attached to the metal blue flag at night, displayed at one or both ends of an engine, car or train, indicates that workmen are under or about it; when thus protected it must not be coupled to or moved. Each class of workmen will display the blue signals and the same workmen are alone authorized to remove same. Other equipment must not be placed on the same track so as to intercept the view of the blue signals, without first notifying the workmen. In yards where switches leading to certrain tracks are power operated, employe in charge must be advised of the track to be used and must block or mark levers in such a manner that switches will not be operated and must not permit movement to such track until advised blue signals have been removed. When it is necessary for an engine to enter a repair track that is protected by blue signals, the engineman must give signal as prescribed by Rule 14(s) and a member of the switching crew must notify the foreman of the repair track, specifying the track to be entered. When emergency repair work is to be done under or about cars in a train, the engineman must be notified and protection must be given those engaged in making the repairs.