Earlier work showed that maximum entropy models can be used to represent surface reflectance spectra of Munsell patches. Here, we introduce a new approach to color constancy which is based upon that work. To our knowledge, all color constancy approaches employing spectral models use linear basis function representations for surface and illuminant spectra. This means that a set of basis functions has to be specified in advance in these algorithms. The proposed maximum entropy approach does not require this a priori information and therefore has a major advantage over other spectral based color constancy approaches. We show that a maximum entropy approach can be used to estimate surface and illuminant spectra given only camera sensor responses. We test our approach both in simulation and experiment. We also show that the performance of the proposed approach is similar to the most successful spectral based color constancy approach. This comparison is carried out in simulation in the presence of noise.