Yes. Fire circles for marshals to know what the material is in case of fire. Required at Le Mans. Yellow is for aluminum. Red is for fiberglass. J6's were painted red on yellow alloy roof by mistake and tried to be wiped off with gasoline which turned them orange.
They are "materials" indicators required at LeMans to let fire crews know what they are dealing with. The roof of the MK IV is aluminum so the "dots" are a different color than the ones on fiberglass bodywork. The roof dots had been cleaned with some solvent at the race and changed color from the original indicated color.