The dyes Methyl Calcein Blue, Arsenazo I, and Xylenol Orange, and the metal salts CuCl2 and NiCl2 were used to generate colorimetric sensors for peptides. Two different approaches were followed: (1) Sensors based on dynamic combinatorial libraries of metal−dye complexes were created by mixing dyes with metal salts in one pot. The optical response of these libraries was analyzed by measuring the spectral changes of the mixtures upon addition of the peptide analytes at six selected wavelengths. (2) Sensor arrays were created from six different metal−dye combinations. The six individual sensors were analyzed at one wavelength, and the resulting data was used as the input for a multivariate analysis. Both types of sensors were evaluated for their ability to differentiate 13 different di- and tripeptides. The sensors based on dynamic combinatorial libraries gave in most cases better results than the sensor array. Furthermore it was found that libraries of intermediate complexity perform best as sensors.