Marshall Selenium Brown is a retouching dye for photos on RC and FB paper Marshall retouching dye is the result of years of research by American company BKA (Brandness-Kalt-Aetna). The Spot-all Kit is designed especially for retouching, coloring and correcting B&W positives and negatives. The colors are completely absorbed by the emulsion and are rapid drying. They can be used on almost all types of film and photo paper, whether it is matte or glossy. White spots caused by dust particles during the developing process can be easily corrected. By mixing the different colors, almost all colors can be achieved.