Reduction with ascorbic acid of tetraethylammonium salt of 18-molybdo-2-phosphate heteropoly complex impregnated on the filter or the chromatographic paper was investigated. Digital scan images of colored paper test strips obtained with the office scanner were resolved into R, G, and B colors. It was found that dependence of the coordinates of RGB colors on the ascorbic acid concentration is satisfactorily linearized using the equation y = y_o + Aexp(–c/t). Rapid and simple colorimetric method for the determination of ascorbic acid based on its reaction with impregnated on the paper 18-MPC was developed. Method was applied to the determination of vitamin C in juices.