In a large bowl, cream butter and sugar until light and fluffy. Beat in egg and vanilla. Gradually add flour and mix well. Divide dough in three portions. Stir the red gel food color and almond extract into one portion. Add neon green food coloring and pistachio oil to the second portion. Add leaf green food coloring to the third portion. Gel food color brands vary in pigment strength, so if your colors are not as vivid as you’d like them to be with 1 teaspoon amount, increase the amount until a vivid color is achieved. If dough is very sticky because of the addition of food color and flavorings, mix in additional flour 1 tablespoon at a time until it loses most of its stickiness.
Roll each portion between two pieces of waxed paper into an 8-in. x 6-in. rectangle. Remove waxed paper. Place red rectangle on a piece of plastic wrap. Top with the neon green and leaf green rectangles; press together lightly. Wrap with plastic wrap and chill until firm, about 2 hours or overnight.
Preheat oven to 375°.
Cut chilled dough in half lengthwise. Return one rectangle to the refrigerator. Cut remaining rectangle into 1/4-in. slices. Place the slices 1 inch apart on ungreased baking sheets.
Bake for 9-12 minutes or until set. Cool for 2 minutes before removing to wire racks. Repeat with remaining dough.
Package in cookie boxes or cellphane bags tied with holiday ribbon.