A method and system implementing the method for color pixel counting in images by determining color pixels that, upon marking, appear as visibly color or gray to the human eye by applying a 2-dimensional filter and a reverse color lookup process. An area color computation is performed on a window around each pixel of interest to determine average gray level values for output colors (C, M, Y). Gray line values for each output color are determined and the values for at least two output colors are compared to the average gray level values. If average gray level value for both colors is within a tolerance for the gray line, the pixel is determined as visibly gray. Otherwise, if at least one count is not within the tolerance, the pixel is determined as visibly color. The count of visibly color pixels can be used to determine the billable color pixel count.