Divide the ingredients into 4 to 5 equal parts before you start. Do this separately for each colour.
In a large saucepan, melt butter over low heat.
Add the marshmallows and continue to stir until the marshmallows have completely melted.
Remove from heat.
Stir in the Rice Krispies, coating them well with the melted marshmallow mixture.
With buttered hands, make golf ball-sized balls and cool to room temperature before serving.
If you want squares or diamond-shaped treats, press the mixture evenly using buttered hands (or buttered spatula) into a 15 x 10 x 2 inch pan, ensuring it has been sprayed/greased or lined with butter paper.
Cut into squares or diamonds when the mixture cools.