A computer-implemented method for quantifying color change of at least one test medium on a diagnostic instrument, the method comprising: capturing with a camera sensor a digital image of at least a portion of the diagnostic instrument which has been exposed to a biological sample, the diagnostic instrument comprising at least one color reference comprising a plurality of reference samples of different colors and a plurality of test media respectively having a plurality of reagents, each reagent changing color in the presence of particular analytes in the biological sample; identifying at least one of the plurality of reference samples, other than a white reference sample, for at least one of the plurality of test media in the diagnostic instrument; characterized by: applying a median filter in a line-wise direction and then in a column wise direction, to the digital image of at least one reference sample and of at least one test medium, to determine a dominant camera-captured color of the at least one reference sample and a dominant camera-captured color of the at least one test medium, respectively; color correcting the dominant camera-captured color of the at least one test medium based on a correction factor derived at least in part from the dominant camera-captured color of the at least one reference sample to determine a corrected test medium color; and comparing the corrected test medium color to a set of possible test medium colors corresponding to predetermined analyte concentrations to determine a test result including an analyte concentration of the biological sample being tested. capturing with a camera sensor a digital image of at least a portion of the diagnostic instrument which has been exposed to a biological sample, the diagnostic instrument comprising at least one color reference comprising a plurality of reference samples of different colors and a plurality of test media respectively having a plurality of reagents, each reagent changing color in the presence of particular analytes in the biological sample; identifying at least one of the plurality of reference samples, other than a white reference sample, for at least one of the plurality of test media in the diagnostic instrument; characterized by: applying a median filter in a line-wise direction and then in a column wise direction, to the digital image of at least one reference sample and of at least one test medium, to determine a dominant camera-captured color of the at least one reference sample and a dominant camera-captured color of the at least one test medium, respectively; color correcting the dominant camera-captured color of the at least one test medium based on a correction factor derived at least in part from the dominant camera-captured color of the at least one reference sample to determine a corrected test medium color; and comparing the corrected test medium color to a set of possible test medium colors corresponding to predetermined analyte concentrations to determine a test result including an analyte concentration of the biological sample being tested. applying a median filter in a line-wise direction and then in a column wise direction, to the digital image of at least one reference sample and of at least one test medium, to determine a dominant camera-captured color of the at least one reference sample and a dominant camera-captured color of the at least one test medium, respectively; color correcting the dominant camera-captured color of the at least one test medium based on a correction factor derived at least in part from the dominant camera-captured color of the at least one reference sample to determine a corrected test medium color; and comparing the corrected test medium color to a set of possible test medium colors corresponding to predetermined analyte concentrations to determine a test result including an analyte concentration of the biological sample being tested.