Visual experiment to try and make something similar to War for the Overworld's different player characters having their own associated costume for their workers. Visually unique designs that still fit onto a singular base skeleton.
In this case, these are all imps, but they follow a specific demon general associated with a different sin.
The green one follows the lord of Vanity, and takes after plants. They're fully confident they'll blossom eventually thanks to the word of their lord, but their lack of knowledge about plants beyond the appearance ensures they can't actually mimic it until they sit down and admit the problem in order to learn more. Their leader knows they'll never do that, though, and leads them along by playing on that insecurity to see them fight tooth and nail on behalf of their lord to feel right.
The red imps serve the lord of Wrath, and look like they're made of pure bone and muscle that allows them to better sense vibrations at the cost of their sight. They trust their leader to guide their petty anger into something productive, but that leader barely even does anything; they're so naturally hateful and resourceful on their own that he knows they'll fight and die to the last anyway. They just need an excuse to let go of that sense of civility.
The lilac imps found themselves under the lord of Sloth, and have skin made of fabric and eyes made of glass. They were promised a painless life free of worry under the lord's rule should they merely sleep within the general's domain, and were given that "life" by being turned into puppets that did everything so the general could do nothing. They can break the strings simply by stirring awake, but seem content not to.
The yellow imps belong to the lord of Avarice. and have a carapace of gold and carbon. Promised untold wealth should they keep digging on the lord's behalf, they were given the material to modify themselves to facilitate this, but in turn had a seemingly insignificant piece of their essence traded, locked inside their lord's hoard in payment. In the end, however, this missing piece is the feeling of satisfaction in their work, and while they dig up treasure after treasure, it's their lord who gets to feel the combined rush, only barely letting them feel it.