It seems like the biggest difference between the two helmets is damage and location of weathering. If you wanted to make and ESB helmet with ROTJ colors, I'd look up all the damage/weathering from the ESB helmet and use that. The main differences between colors seem to be that the black inner mandibles of the ESB helmet have more of a dark bluish tint on the ROTJ version, and the earcaps on the ROTJ helmet are silver/metal, rather than tan on the ESB helmet.
There are lots of photos up in the gallery showcasing both the ESB and ROTJ helmet, so you could just take the elements you like from each helmet and create something that works for you! Good luck!