The optical properties of gold nanodisk arrays prepared by colloidal lithography are studied experimentally. The arrays exhibit short range translational order and weak interparticle interactions. Tunable localized surface plasmon resonances are achieved by varying the diameter of the disks at constant disk height. The macroscopic optical properties are well-described by modeling the gold disks as oblate spheroids in the electrostatic limit. The optical sensing capabilities of the disks are investigated by varying the surrounding refractive index. It is found, in agreement with theory, that more oblate disk shapes have higher sensitivity. This suggests that nanodisks prepared by colloidal lithography are of interest as substrates for optimizing optical biosensing; methods at the nanometer scale.