According to an aspect of the present disclosure, a color sensor is provided for sensing whether a ground roller in a corona treatment system needs to be serviced. The color sensor is capable of detecting imperfections which have changed the reflectance level of the ground roller from a predefined level. According to another aspect of the present disclosure, if a determination is made that the ground roller needs to be serviced, then an alarm is activated and/or the operation of the corona treatment system is ceased.