In our little group we had black kneepads so white chinagraphs.
As an aside, whilst on the above det the DZSO, who got himself into several scrapes was briefing boat troop by 2 Gemini craft. He indicated to the boys which would be despatched first. "Get a piece of chalk from the Nav to mark the boats" he said.
"Wot do you think I've got up here? a blackboard? I cried.
He came over and said "Don't ridicule me in front of the troops"
When he got back, he saw that the troops had found some clay and had written on the geminis: BOAT 1 on the first and NOT BOAT 1 on the second!
It would take a heart of stone.