The technician said that the machine is sanitizing properly when the iodine sanitizer turns the color of the paper because the concentration is

The answer is because the concentration of iodine sanitizer is immersed by the paper. If the paper has immersed in the iodine sanitizer, it could produce a color change - - where in, it could conclude that the paper has been sanitized properly as the color signifies that it has already been mixed with iodine, therefore, it has already been sanitized.