I too like to keep my D&D monsters recognizably D&Dish, but with my own personal touch. For a few examples, I keep my dragons color-coded, but my metallic dragons are lead, tin, copper, iron, silver, quicksilver, and gold, and my chromatic dragons are black/negro, white/albino, yellow/citrine, and red/ruby in reference to the alchemical metals and stages of the Magnum Opus. My mind flayers are Aboleth larvae introduced to a humanoid’s cerebrospinal fluid before maturity, their ceromiphasis causes their tentacles to burst through the host’s skull without transforming the whole host into a purple octopus-man, and my Elder Brains are the brains of fully-mature Aboleth preserved outside of their original body after its death. And my Beholders, rather than being hatched from eggs barfed out by other Beholders or imagined in other Beholders’ dreams, are much more like the creature inside a Dalek’s armor; genetically-engineered beings, created with the specific intent to be the ultimate life form, and to enslave or exterminate all lesser forms of life.
EDIT: Only tangentially related, but it occurs to me that the Ood from Doctor Who are totally Mind Flayers. WHICH ONE OF THE DR WHO WRITERS IS A D&D NERD???