Info on C.S.A.R. Signalling :-
Distinctive Features of the Signals and Levers.
"Although generally the signals in the Cape and Natal conformed to British practice, the C.S.A.R. retained some of the features in use under the old Transvaal N.Z.A.Z.M. administration. The C.S.A.R. altered the signal arm to be square-ended and painted its front white with a red disc, and its back, black with a white disc. The distant or “through” signal arm was fish-tailed and painted white with a red fishtail on the front and black with white fishtail on the back. The signal posts were painted with distinctive colours, viz :- white for starting and advanced starting signals, red and white alternately for home signals, green for outer home signals (single lines), and top half green and bottom half white for “ through“ or distant signals. This system of painting the signal posts in various styles was adopted to assist drivers in distinguishing the class of signal they were approaching, particularly in the case of the outer home, as its arm was square ended, the same as a home signal arm. At night time, however, the “through” signal displayed a yellow light in the “on” position, but all other signals showed red lights when normal. This is apparently the earliest instance of the yellow light being used for main line service in the British Empire: When a signal was cleared, a green light was seen".
S. Starkey (Chief Signal Engineer) S.A.R. & H.1941