The otyugh is one of those D&D monsters that doesn’t come from folklore, literature, or any identifiable source other than Gary Gygax’s imagination.* The Monster Manual doesn’t give any indication of their coloring, but given their habitat of offal, refuse, and dung, I’m thinking brown or red-brown.
So here’s a sort of step-by-step guide to how I painted mine. The minis I had were two Grenadier Otyughs (one I’ve had since the 1980s and another Scottsz gave me); a TSR neo-otyugh (purchased very cheaply at Origins 2006); and a TSR Otyugh (also a gift from Scottsz).
1. Sprayed with grey primer.
2. Painted with somewhat thinned Burnt Umber craft paint (I use Ceramcoat mostly).
3. Dry brushed with a mix of white and burnt umber.
4. This is where I got sloppy and stopped photographing each step. I painted their eyes, mouths, and bases black, and then dry-brushed their tentacles a mix of pink and (Caucasian) flesh. Then I gave the tentacles a wash of thinned down Citadel red ink. (I bought a set of their inks in about 1989 at NeoVention. I don’t use them that often and still have them. They never dried out!)
5. The finished minis. I painted white eyes, spines, teeth, and claws, and inked the edges of the mouths red, and gave the neo-otyugh a pink tongue. In hindsight maybe a little yellow would have enhanced the teeth. I don’t think they actually brush or floss.
Having two Grenadier otyughs let me use one as a ‘rough draft’ while figuring out the paint scheme.
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*There was some speculation, maybe at Dragonsfoot or some blog, that the otyugh was partly inspired by the ‘garbage disposal monster’ in the first Star Wars movie.
Swords & Dorkery 
Very nice work! They look a lot more intimidating as a group!
Solid work! I like these paint jobs.
Thanks!
Oh Dear God one of those looks like a butthole with teeth! Aieee!!!!!
The neo-otyugh: eats and lives in poop, is an anus with teeth, may or may not be highly intelligent…Hmm, I think it runs a blog…YDIS
They look great !