Those colours reminds me of popular colour choises from my early 20's. Black red or black green. I do not like combining all 3. Espeally on miniatures I think red and green ends up looking very flat. While they are on opposet sides of the colour spectre, scoring a 100% on ittens colour wheel, they score a bit bad on an intensety scale. They are both a 5 on the intensaty. Purple is a 1, and yellow had a full score of 9. So purple and yellow 'fight' a lot more. If you go blue an orange they had a 3 and a 7 and they are stil in contrast but less so. And then red green is 5 and 5. I do not remember the name of this scale, it still bothers me that I remember the theory but not the name.
Anyway, on the model the red and the green are not so far apart, or the surfaces are to small in my subjective opinion. Perhaps you can try a purety contrasts? With very brown or grey colours. I think particularly grey colours that still contain some colour in them could be really good. Think like how Warpfiend grey is stil a purple, even though it is grey, as opposed to mechanical grey that is mostly white and black in the spectrum.
I would try some test colours on the scything tallons if you have a carnifex. Personally I would try 2 schemes:
Red black, with a very brown orange.
Red, black, with a very grey green. (It would put the red and the green in more of a contrast.)
Or, with skills like yours, you can do a very nice black and red model with just 2 colours. Perhaps you could do some red lines along the charapace.
This is Phil Kelly's old 2 colour scheme. Bana yellow and black. But red would do as well.
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