Maybe the red pigment was red lead? That would probably fall foul of todays H&S legislation. I can remember when the chandlery at Woolverstone used to sell red lead putty, they had a great big tub of it and Vic would say, "how much do you want", "half a pound please Vic", he would then just ladle it out into a plastic bag with his hand!! Great stuff for filling seams on a 1930s wooden boat.