The article considers relief computation for computer-synthesized holograms creating full-color images. The propagation of radiation from the optical element to the focal plane is described by scalar wave theory and is considered both in the long-focus approximation and in the geometrical optics approximation. The phase function specifying the optical element is from the set of admissible phase functions defined by purely technological constraints. A composite phase element is constructed in the geometrical optics approximation. The algorithms rely on numerical solution of the inverse problem in the long-focus approximation and on the analytical form of the phase function in the geometrical optics approximation. The optical elements generated by the proposed procedure have been manufactured by electron-beam lithography. Their comparison has shown that the composite phase element is much more efficient.