And finally, the dorsal view. I saw Bob's recent post of this species and remembered this individual. Many months after photographing this individual, I read an account that may explain why the coloration varies from green to black.
Hogue describes the process in a related species, Dynastes hercules
, in Latin American Insects and Entomology (1)
. I'm assuming the process applies to our species as well. The color may change to and from black within a few minutes and seems to be controlled by humidity. There's also a suggestion that the beetle may have some control over it. A layer beneath the outer cuticle of the elytra reflects yellow (for that species) when dry. When saturated, it permits the black underlayers to show through.
Hinton, H. E., and G. M. Jarman. 1973. Physiological colour change in the elytra of the Hercules beetle, Dynastes hercules
. J. Ins. Physiol. 19:533-549.