Well, as there is such a huge range of skin colours in humans, why not Martians too? As the first encounter I had with Mars was with John Carter, I'd be happy to use any of the colours Burroughs does.
I quite like the dark yellow shade you have done on a couple of your Parhoon Rifles, but that's just me.
As Herby said, it's VSF - do what
you feel like doing