The synthesis and characterization of highly ordered three-dimensional photonic crystals have been the subjects of intense study over the past two decades due to the unique ability of these structures to control light at the nanoscale. Building on that work in recent years, increasing interest is now focused on the unique optical properties of disordered and quasi-ordered photonic structures. We present a study of the effects of shape anisotropy and disorder on the specular reflection properties of polymer-based colloidal films comprised of rod-shaped subunits of varying aspect ratio. We characterize the specular reflectance properties of these films as a function of their increasing levels of disorder, demonstrating progressive transition from resonant reflection to diffuse reflection. The onset of the diffuse reflection is governed by particle size.