We propose a new method for approximating object colour solids, which we call Optimised Spherical Sampling. We compare our new method to the previously described methods based on 1) the two-transition conjecture of Schrodinger and 2) Random Spherical Sampling. The proposed method is based on the approximation of the OCS local error at every face of the volume and its subsequent optimisation. We find that the new method produces a significantly less error for the same number of samples than the two prior art methods.