I knew only the mandellii's the base of the lower mandible is of limited light color. By the way, Ayuwat's images are quite wide in the bright part of the lower mandiblel. The bright color range of the mandellii's lower mandible base is what I've always wondered about.
I don't see much variation in his images myself - the base is a kind of yellowish flesh colour. I'm not sure how many individuals are shown in these images, but as he saw 7 that day, I imagine it's more than one.