A plurality of groups of colorimetrically distinguishable metal nanoparticles are prepared to label specific analytes whose presence in a sample is under investigation, each group for specific analytes. After being mixed with the sample so that labeling can occur if the analyte or analytes are present, the sample is exposed to a sensor having probes for the analytes under investigation. Binding of any of the analytes present will carry the metal nanoparticle as well, which then enables colorimetric detection of each label to determine which if any of the analytes is present in the sample. In an alternative method the probes can be labeled with calorimetrically distinguishable metal nanoparticle labels and any binding events can be detected calorimetrically.