In a bowl mix together the icing with the green food coloring until desired "monster green" is reached. Put the frosting in a pastry bag or resealable plastic bag fitted with pastry tip. Pipe a haphazard squiggle pattern on top of the cupcake until completely covered and slightly mounded. Put a green gummy ring on top. Create eyes for the monster by putting 2 brown coated candies into the center of the green gummy candy. Repeat with the remaining cupcakes.
Use cashew nuts to create horns by inserting them into the frosting behind the eyes with the smaller side facing up. Repeat with remaining cupcakes. Arrange the cupcakes on a serving platter and serve.