We report an image-based detection of horseradish peroxidase (HRP) by different color spaces. The results show excellent correlation between color saturation and absorbance (Pearson correlation coefficient; 0.9868) with respect to HRP. The present method can detect 185 and 46.45 fg/ml of HRP using o-phenylenediamine dihydrochloride and 3,3',5,5'-tetramethylbenzidine as chromogenic substrates respectively. (C) 2014, The Society for Biotechnology, Japan. All rights reserved.