Dynamic light scattering experiments are reported on crystal-like ordered colloidal suspensions composed of two types of electrostatically interacting particles having similar size and effective particle charge. The particles differ only in their refractive indices. We obtain the incoherent (self) intermediate scattering function of these mixtures by using only a trace concentration of one of the species and matching the refractive index of the suspending liquid medium to that of the other. Localization of the tracer particles about randomly located lattice sites of the colloidal crystal is manifested in the nonergodicity of the incoherent intermediate scattering functions. The latter, and the particle mean-squared displacements obtained from them, plateau to finite values at long times. In analogy to neutron scattering these plateau values of the incoherent intermediate scattering functions may be called the elastic incoherent structure factor.