the excess red dye is removed the application and excess dye solution removal is repeated until the damaged area is no longer visible through the red loss filter again it is noted that he damaged area is still visible to the naked eye as the undamaged area is still yellow dye deficient in one embodiment following the blue dye and red dye application the applicator uses a yellow loss filter or a short pass filter that transmits light of wavelengths shorter than approximately 450 nanometers to determine yellow loss in the damaged are when looking at the damaged area through the yellow loss filter if a damaged area is still visible it is an indication that there is yellow loss in the damaged area thus while viewing the damaged area through the yellow loss filter the applicator repeatedly applies and extracts the working yellow dye solution to the damaged area until the damaged area is invisible through the yellow loss filter when the blue red and yellow working dyes have all been applied until the damaged area is invisible according the respective color loss filters the damaged area should visually match the undamaged area fig1 illustrates one embodiment of typical gray scale comparator cards to determine the proper working dye solution in this additional embodiment the gray scale system consists of ten cards indicating working.