Thanks for the reply Mike. I'll post some snaps tonight. It does have a grey card, a diffuser and separate knobs for yellow, cyan and megenta (and another that I can't remember the descriptor). The display is an analog needle with a 0 in the middle with numbers ascending/decending on either side.

After using my black and white darkroom for many years, I decided it was time to expand my horizons! RA-4 is so much fun, but my brain has to be reprogrammed for CMY