def remove_red(image)
   num_rows = image.length
   num_columns = image[0].length
   for row in 0..num_rows-1 do
      for column in 0..num_columns-1 do
         green = image[row][column][1]
         blue = image[row][column][2]
         image[row][column] = [0, green, blue]
      end
   end
   return nil
end