Coloured butters:
Rather use butter than margarine as margarine tends to soften quickly at room temperature causing the sandwiches to look unappetizing after a few hours.
Yellow butter: Soften the butter and mix with one of the following: Yellow food colouring, finely grated cheese, hard boiled egg yolk, mashed
Red butter: Tomato sauce (ketchup) or tomato paste
Green butter: [...]


