Colorimetric staining techniques such as immunohistochemistry (IHC), immunofluorescence (IF) and histochemistry (HC) provide useful information regarding the localization and relative amount of a molecule/substance in skin. We have developed a novel, straightforward method to assess colorimetric staining by combining features from two open‐source software programs. As a proof of principle, we demonstrate the utility of this approach by analysing changes in skin melanin deposition during the radiation‐induced tanning response of Yucatan mini‐pigs. This method includes a visualization step to validate the accuracy of colour selection before quantitation to ensure accuracy. The data show that this method is robust and will provide a means to obtain accurate comparative analyses of staining in IHC/IF/HC samples.