The only thing I could find on distinguishing the subspecies was here
http://www.herper.com/snakearticles/diadems.html where they claim that S.d cliffordi has less subcaudal scales than S.d diadema (S.d atriceps) but I'm not personally familiar, so I can't say for sure whether that's true or not. The ratsnakefoundation page on S.d cliffordi gives more information on the species, so maybe something there can help you.
http://www.ratsnakefoundation.org/in...iadem-ratsnake
Info on these fascinating guys is hard to come by, so please share what you learn by keeping them! I'm especially curious about the timeline of their color change. I seem to only see them as one or another, never in a transitional phase, so maybe I'm missing something... The only adults I ever saw were at an expo. The pair was a gorgeous orange with sharp contrasting blotches and they blew me right away! They're definitely on my wish list, but I'm going to wait until I see more captive bred for sale. ~Someday~
Best of luck with your pair! It's nice hearing they're so spunky, I hope they thrive for you!