I know it's dangerous to use four different colors. Let me know if I've gone too far or if I'm still within the lines of sanity here. Any brilliant suggestions would be... brilliant.
It's not dangerous to use 4 different colors. It's dangerous to use the WRONG four colors! :)
Let's look at the model:
And let's map out the colors:
Ok, so most of the model is painted in an analogous red-orange range. But you also have a green-magenta complement going on with the weapon hose and the lash whip. That's what's throwing you off.
So you need to decide whether you want hue contrast in your model, or if you want it all to blend together. Assuming you want some contrast, I'd do what you did with the eyes and make all your contrasty bits a bluish-cyan instead of magenta or green. Because that's the complement (opposite) of the red-orange hue range that most of the model is painted in.
But that also seems like a bit of a stretch. Why are you drawing attention to that weapon hose anyhow? What's so special about it? Pretty color combinations are one thing, but you should have a reason for why certain bits are going to contrast to the rest. Else it just comes off as meaningless noise.