Beat butter, baking soda, salt, sugar and eggs in a large bowl with a mixer on medium until creamy. On low speed, beat in 2 cups of flour until just blended.
Remove 1 1/2 C dough to a medium bowl; stir in vanilla and cocoa until no white streaks remain.
Stir peppermint extract and remaining 1/2 cup flour into plain dough. Add about 10 drops of food color. Beat until no white streaks remain. Cover doughs and refrigerate 30 minutes, until firm.
Roll chocolate dough into fat log. Divide into quarters. Working with 1 portion at a time (wrap and refrigerate rest) roll into 3/4-inch-thick rope. Spread red nonpareils on a sheet of wax paper. Roll rope into nonpareils to coat; wrap rope in foil. Repeat with remaining chocolate dough, then the green dough and green nonpareils.
Place ropes on a cookie sheet; refrigerate at least 2 hours, or until firm enough to slice neatly.
Heat oven to 350°F Have ungreased baking sheets ready.
Slice 1 rope at a time into 1/4-inch-thick rounds. Place 1 inch apart and bake 8-10 minutes until done.
Remove to wire racks to cool.