I'm quite certain we had a white or yellow refill in ATC at Marham. There wa a floodlit board and each flight had a peice id perspex written from behind with the skippers name, the airframe no , the fuel load and what the detail was, The writing was about 2 inches high, with a black background and floodlit from behind. On the other side of the airfield in the Self Briefing room in Ops there was copious amounts of propelling chinagraphs but only black or red refills.. I've got one as a keepsake from Shackletons along with the STR HF Radio Tuning tool.(unused)