So here's some more screenshots of colorful Creatures that have been born in my feral run.
HAHAHA his ridiculous mutated legs.
The common mutation has been the purple and green, which is a mild pigment swap. The turquoise and purple mutation is a more intense pigment swap, and showed up just recently in the population.
The one on the left has a pigment swap. The one on the right has the same pigment swap, but also has a pigment rotation, making the parts that would normally be greenish a dull grayish purple.