In a microwave or a large saucepan over low heat, melt marshmallows, oil and, if using, extract; stir until smooth. Remove from heat; remove half the mixture to another saucepan over low heat.
Stir in the green coloring; add 3 cups cereal and stir to combine. Stir the pink coloring and red coloring to remaining marshmallow mixture; add remaining 3 cups cereal and stir to combine.
Press half of green mixture around inside edge of a lightly greased 9-in. round cake pan, using waxed paper or a lightly greased spatula. Pack the center with half of pink mixture; press half of the chocolate chips into the surface of the pink portion. In a second cake pan, repeat with remaining mixtures and chips. Cool to room temperature. Cut each portion into 12 wedges.