I was able to borrow a GMT 116710 BLNR from my pals at Fourtané for an Everest Strap review on A Blog to Watch. While I had the 116710 BLNR, I made some quick comparisons to the Explorer II 216570.
The blue–black bezel is a first in the watch industry and known within the Rolex cognoscente as the Rolex BMT Bruiser or GMT Batman because of its iconic colors. Solid colored ceramic bezels are nothing new to Rolex, but the GMT BLNR (BLNR for Bleu/Noir or blue/black) is the first time two colors are incorporated into one ceramic bezel insert by any Swiss watch company, and the research Rolex pursued to accomplish this feat is well worth the effort.
I have more on this posted at Minus4Plus6.com - Explorer II & GMT II - C