Some discussion on the colour of navigation side light, light boards. About 1975, the MoDn altered all the side light housing to comply with the 1972 regs which had just been ratified, from red and green colour to matt black, also for the first time the cut off point for seeing these lights had to be from 22.5 degrees astern to dead ahead, the most critical being ahead, i.e if you were one degree past the ahead or from it you only saw one light, so you only saw the dreaded triangle absolutely dead ahead of a vessel, this was for safety considerations in the collision regs. So only Puffers in preservation and about three in number which did survive on the Clyde in trade until the late 1970's actually have black side light boards.