Well, a green or brown would do the trick in my opinion. Could probably start with something like rotting flesh then shade it darker with a wash. It will fill in all the unique gaps that kroot models look to have, around the bones carapace arms and in there. Apply highlights as what your eyes fancy I guess. Paint the armor and weapons however you would like
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Could probably play with little things like the highlights on the gap areas and the hair (Ermmm spines....). Keep in mind they do have beaks and carapace on the belly...
Do some searches on CMON though and maybe do some background research on what kroots are... From a simple search on wikipedia about kroot I came up with this...
\"The Kroot, while humanoid in appearance, are believed to have evolved from a carrion-eating avian form, as they possess vestigial beaks and a light bone structure. They have four digits on their hands (arranged in a zygodactylic form) and feet. While tall and wiry, they have an extremely strong musculature, coupled with quick reflexes, and are stronger than humans of equal size and weight. Their heads are crowned with tough quills that form part of their sensory apparatus; these connect to the brain via ganglia. Kroot eyes have no pupil, are generally milky white in colouration, and can see into the infrared spectrum, allowing Kroot to track their prey by body heat.
Kroot do not urinate or defecate. This is because they possess an incredibly effective digestive system. What cannot be digested is regurgitated, and some chemicals are released as a thick sweat. This sweat has slight heat retardant and antibiotic properties, and can be altered by the Kroot to exude a variety of pheromones. These pheromones can be controlled and altered, and are a component of the Kroot language. They are also used to control other animals, mark territory or trails, and (according to one Tau researcher), are a component of Kroot humour towards outsiders.
One of the most peculiar biological traits of the Kroot is their ability to rapidly evolve, with the capability for significant changes over four or five generations. The digestive system of the Kroot is able to extract DNA from their food, which is then incorporated into that particular Kroot\'s DNA structure. Selective breeding ensures that these consumed traits become present in later generations. However, this is not without risk, as the new traits can be accompanied by a loss in sentience, and some Kroot have been trapped in evolutionary dead ends.\"
Because they literally evolve from what they eat (much like tyranids do if I remember correctly...) and their ability to rapidly evolve they could come out with some really unique and cool conversions... At the same time their evolution leads you to choose how to paint them. This leaves the door wide open to your choice, customize paint them how you want.
Keep in mind any particular theme you want or if you want maybe integrate something cool about another race into their form. Also Keep in mind little things, like the fact that kroots sweat a congealed liquid... so they might be slimey in some areas if they are in intense combat. Keep in mind they eat flesh ravenously, blood on the beaks, bits of flesh on the bases or hanging from the mouths might be an idea. So many things you can do, they really are cool from what I have read. They will even choose what they eat based on their need to evolve... Thus is the roll of the shaper... Perhaps a good pose for a shaper would be inspecting fresh \"Meat\" ... Just thoughts...
Oh and heres a couple pictures:
Kroot 1
Beautiful Blue Kroot
A Kroot Shaper