When the case demands a high strength zirconia material and the restoration is in the secondary smile zone (shadows of the smile), then I am thinking pre-sintering infiltration coloring. As of late, my preference is the ZirCAD LT Colouring Liquids. This video will show the steps and liquid color application technique I use for a premolar bridge. My primary coloring objectives for green zirconia is creating the saturation multi-effect and lowering the value in the cusp and occlusal zones. It rather simple to learn and master.