We discuss how to simulate numerically the far-field propagation of the spectrum of light by propagating the cross-spectral density for a planar light source with a given coherence model. To test our approach, we performed simulations for two source models: a Gaussian Schell-model source and a nonuniformly Gaussian-correlated source. We show that our algorithm correctly reproduces the theoretical solutions by Emil Wolf for planar Gaussian Schell-model source, namely, the spectral shifts of spectral lines due to source correlations. Our approach can be used for two-dimensional source models in which the spatial coherence components are frequency independent. It can also be used for nonhomogeneous extended sources of partial coherent light.