Resonance domain diffractive optical elements for combining RGB laser beams into a single collimated beam were designed, fabricated, and experimentally investigated. The input RGB beams were angular separated up to tens of degrees and set in a nearly Bragg arrangement for high diffraction efficiency. A single resonance domain diffractive lens delivered beam combining and collimation functions with reasonable residue divergence. The resonance domain diffraction grating delivered diffraction-limited residue divergence in combining the collimated RGB beams. Optical experiments with fiber-coupled RGB lasers and e-beam-fabricated beam combiners proved low residue beam divergence, a high polarization extinction ratio, and total measured diffraction efficiency of about 80%.