A poly(styrene-co-acrylamide) (PS-AAM) latex was prepared by emulsion polymerization and purified by sedimentation of colloidal crystals. These were diluted and dried on a mica substrate forming submonolayers that were examined by atomic force microscopy (AFM), scanning electron microscopy (SEM), and nearfield optical microscopy (SNOM). The images show domains of at least two particle types clustered within the films, in every field examined. Zonal centrifugation of the colloidal-crystal forming particles still produced three separated fractions, two of which were further cast into uniform submonolayers. These results show that latex particles have a strong tendency to cluster with identical particles even in the presence of other, similar particles. However, colloidal crystal formation has a limited tolerance to particle heterogeneity but the quality of the dry macrocrystals is strongly dependent on particle uniformity.