1. A method for processing an image of a color form having respondent information entered thereon to remove a color background from the form, said method comprising: executing software program instructions with a processor to perform the steps of: retrieving a template image of a blank form, the template image comprising a plurality of pixels representing the form without any respondent information entered thereon; retrieving a respondent image of a completed form, the respondent image comprising a plurality of pixels representing the form and the respondent information entered thereon; registering the respondent image against the template image to establish correspondence between pixels of the respondent image and pixels of the template image; determining whether to keep the pixels in the respondent image by applying a geometric solid threshold comparison with respect to their corresponding pixels in the template image, wherein the geometric solid threshold comparison assesses both color similarity and relative darkness between corresponding pixels in the respondent and template images, and wherein the geometric solid comprises one of a paraboloid and a cone; and removing pixels from the respondent image based on the geometric solid threshold comparison to obtain a color form dropout image including pixels only associated with the respondent information.