3D printing enables the production of objects that combine materials in hitherto infeasible ways, with the potential of varying their use with a granularity of up to individual print-resolution voxels. By combining printing materials, such as powders, fluid agents, etc., in volumetrically different ways, a limited number of materials can be used to yield a great variety of object properties, such as stiffness, strength, density, translucency and color. A key challenge is to ensure that an input object with volumetricallyspecified properties is appropriately transformed to yield per-voxel recipes for how to combine a printing system's materials. To ensure that such a transformation is performed in a way that maintains volumetric control with up to voxel precision, the present paper introduces a content processing pipeline that has individual printed voxel contents as its basic building blocks and that controls their placement in a natively volumetric domain. This pipeline is an evolution of the HANS print control paradigm [1]. First results, applied to control color of 3D printed objects are reported.