In medium bowl, crumble dough; stir or knead in flour until well mixed. Divide dough into 3 equal portions. Place 2 dough portions in 2 small bowls. Stir or knead in green gel food color into 1 bowl and red gel food color into other bowl. Leave third dough portion white. Drop tablespoonfuls of all colors of dough in random pattern into pan. Press dough evenly into bottom of pan so that each color just touches.