A method of watermarking print ready image data used in the commercial packaging industry is described. A significant proportion of packages are printed using spot colors, therefore various tools to support watermarking spot colors are required. Previously we have described a method which assumes that the package design contains process colors CMY as well as the spot colors to insert a chrominance watermark. Some package designs do not include the process colors CMY or are being printed with a print process which allows limited overprinting, and require a different approach. For simplicity of press control, a binary watermarking system was developed. The binary watermark is inserted in a single ink color with values of 0 and 100%. For the binary watermark to be used in a package design, a method is required which evaluates the ink colors used in a package design and ranks them for use with a modern barcode scanner at the Point of Sale (POS) station.