A measure for objectively assessing the performance of color image fusion methods is proposed. Two different aspects are considered in establishing the proposed measure-namely, the amount of common information between the source images and the final fused image as well as the distribution of color information in the final image in order to achieve optimal color representation. Mutual information and conditional mutual information are employed in order to assess information transfer between the source images and the final fused image. Simultaneously, the distribution of colors in the final image is explored by means of the hue coordinate in the perceptually uniform CIELAB space. The proposed measure does not depend on the use of a target-fused image for the objective performance evaluation. It is employed experimentally for objective evaluation of fusion methods in the cases of medical imaging and night vision data.