Two types of films that are structurally colored by exploiting the self-assembly of colloidal polymer nanoparticles were created. Monodisperse PS spheres were synthesized using a surfactant-free polymerization technique. Particles were electrostatically stabilized by copolymerization with sodium 4-vinylbenzenesulfonate. After synthesis, particle suspensions were washed by centrifugation and resuspension at least three times with deionized (DI) water. Particle sizes were determined by SEM image analysis with an accelerating voltage of 10 kV, after being coated with a thin layer of gold. To prepare bidisperse suspensions, equal volumes of two monodisperse suspensions were mixed by pipetting approximately 20 times and vortexing for at least 30 s. It was observed that isotropic structures with a characteristic length-scale comparable to the wavelength of visible light can produce structural color when wavelength-independent scattering is suppressed.