MICROWAVE 6 oz. of chocolate in separate medium microwaveable bowls on HIGH 2 min., stirring after 1 min. Stir until chocolates are completely melted.
MIX desired food coloring into each bowl of melted chocolate until well blended. (Or, tint just 1 bowl of melted chocolate, keeping second bowl of melted chocolate white.) Alternately spoon tinted chocolates onto wax paper-covered baking sheet or tray. Tap baking sheet on table top to evenly disperse chocolate. Swirl colored chocolates with knife several times for marble effect.
REFRIGERATE 1 hour or until firm. Break into pieces.