Hard question, especially if you reject black and grey and we try to remain within the Doom palette.
"Mauler" is also a weapon in Strife that fires green energy, pertaps make a bright green Demon?
Hey, it'd at least be novel.
(And of course you've gotta adjust the blood on the death sequence sprites.)
Which could be done with relative ease by making a mask out of the original Pinky, or preforming the recolor via Slade3 and pasting the Pinky blood back onto it.
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