A blueprint is a type of paper-based reproduction. For almost a century blueprint was the only low cost process available for copying drawings. Despite today this technology has been largely superseded by digital printing, it is still being used in emerging countries. When making copies of those documents, the colored background often makes difficult reading the information in the scanned plot. Hence, having an accurate way to transform the background to white enhances the look of the plot, plus saves ink when printing. This paper introduces an algorithm for removing the background color from a blueprint scanned image, comprising processing the image in a colorimetric space by determining the colorimetric values of the background color of the image, computing a linear chromatic adaptation transform for transforming the background-color colorimetric values to values of a target white point, and applying the computed chromatic adaptation transformation to the image.