1. A processor-implemented method for color pixel counting in documents for billing comprising at least one page of image data using an image processing apparatus, the image processing apparatus comprising at least one processor for processing documents containing image data comprising a plurality of pixels, the method comprising the following acts implemented by the at least one processor: receiving image data of a document comprising a plurality of pixels; determining a billable count of color pixels in the received image data by determining if color pixels from the received image data are visibly color or composite gray to the human eye upon marking using one or more output color components by processing pixels of interest, and, for each pixel of interest: establishing a window in the image data comprising the pixel of interest and neighboring pixels around the pixel of interest; performing an area color computation of the window to determine an average gray level value for each output color component for the pixels in the window; determining gray line values for the output color components at which they appear visibly gray to the human eye when marked; comparing the average gray level value from the area color computation for at least two output color components to corresponding gray line values, and, wherein the comparing determines that the pixel of interest is visibly color or composite gray upon marking.