There are provided embodiments for a three-dimensional ultrasound Image based on a three-dimensional color reference table. In one embodiment, an ultrasound system comprises: a storage unit for storing a three-dimensional color reference table for providing colors corresponding to at least one of intensity accumulation values and shading values throughout depth； and a processing unit configured to form volume data based on ultrasound data corresponding to a target object and perform ray-casting on the volume data to calculate intensity accumulation values and shading values throughout the depth, the processing unit being further configured to apply colors corresponding to the at least one of the calculated intensity accumulation values and the calculated shading values based on the three-dimensional color reference table.
