Robe fixtures homogenise beams really well but, for the ultimate smoothness, most of our pixelated LED wash lights can easily be fitted with a Fresnel Wash (FW) diffusion filter in-between the LED array and the lenses. They can also be ordered pre-installed if desired, as FW versions. 

The Fresnel Wash diffuser smooths out the constituent colours, even more, producing a consistent, totally homogenised, one colour beam with a smoother edge at narrow zoom settings.