In a large mixing bowl, cream butter and sugar. Beat in egg and extract. Combine the flour, baking powder and salt; gradually add to creamed mixture. Set aside 1 cup of dough.
Tint remaining dough red; shape into a 3-1/2-in.-long log. Wrap in plastic wrap. Tint 1/3 cup of the reserved dough green; wrap in plastic wrap. Wrap remaining plain dough. Refrigerate for 2 hours or until firm.
On a lightly floured surface, roll plain dough into a 8-1/2-in. x 3-1/2-in. rectangle. Place red dough log on the end of a short side of the rectangle; roll up. Roll green dough into a 10-in. x 3-1/2-in. rectangle. Place red and white log on the end of a short side on green dough; roll up. Wrap in plastic wrap; refrigerate overnight.
Unwrap and cut into 3/16-in. slices (just less than 1/4 in.). Place 2 inches apart on ungreased baking sheets. Cut raisins into small pieces. Lightly press raisin bits and sesame seeds into red dough to resemble watermelon seeds.
Bake at 350° for 9-11 minutes or until firm. Immediately cut cookies in half. Remove to wire racks to cool.