Edible dye used to colour food. Frequently used to make coloured icing for cakes or to whip up a batch of green eggs and ham without risking food poisoning. Food colouring is also sometimes used as cheap body paint. Beware - it takes one hell of a bath to get it out of your skin. I used green food colouring once to evoke nausea in a school project lampooning Jacques Cousteau, and I was green for days afterwards. Some people have allergies to food colouring, particularly the kind containing red dye.