Hmmm, maybe, I'm not a grouper expert. But i never found images of one of this colour until now. Why E. flavocaeruleus should be ruled out? I cannot find differences...
It's actually not as much as a colour matter than you might think. Flavocaeruleus has a shorter snout and the first half of the fish is significantly fatter than marginatus. For this last one everything is a bit more in proportion, while for flavocaeruleus it looks like the head is the biggest part of the fish. When it comes to colouration, flavocaeruleus is blue with a touch of yellow on the pectoral fins (even for captive animals there is almost always a bit of yellow). Marginatus on the other hand is extremely variable, going from the typical brown specimens with white spots to a more subtle fish with a greyish/brownish shine (like the animal above). Some specimens even have yellowish spots! I recommend the book Europe and Mediterranean Marine Fish identification guide, it gives a great impression of the many variable patterns of marginatus. It's for me also the best book out there to identify species from Europe and the Mediterranean.
I hope this answers your question
