Terranaut: Cast Colors (Patreon)

Getting ahead of myself with this, but I wanted to make sure the cast's coloration makes them easily distinguishable regardless of the lighting situation. Lower attenuation of red and UV wavelengths underwater means that in certain situations, they all become monochrome. Brr-kt's tattoos and engravings are colored specifically to pop on land and disappear in water,it's a reference to their passion for terrestrial engineering.

The fact scuds are much less brightly colored in the water is actually an evolutionary quirk. The recent ancestors of scuds were coastal/intertidal scavengers with a higher predatory threat on land than in the water, so being able to stick together in bands and keep track of each other while foraging above water was important for staying safe. Meanwhile under the water surface, scuds were usually the biggest predators in the rocky shallows, so sneaking up on prey was more important than keeping track of fellows. 

This goes hand-in-hand with their body plan: despite being obligate amphibians, scuds are much faster moving on land than on water. Sprinting back to water away from a terrestrial predator was historically more important for their lineage than improving upon their relatively slow seabird paddle.