Prepare and fry donuts according to the directions on the bag. Let cool completely. Heat the white flat icing and separate into two bowls of equal amounts. Add pink food coloring to one bowl and yellow food coloring to the other until the desired shades are reached. Split donuts into two equal batches. Dip the first half of donuts with the pink icing and the second half of donuts with the yellow icing so that the icing evenly coats the top. Immediately sprinkle the tops of the donuts with colored mini marshmallows.