Ok, I have one more suggestion for you to consider!
In Imperial Armor Modeling Masterclass 2, they describe but unfortunately don't show how a Saim-Hann Phantom titan bust was painted by laying down a shading undercoat in a monotone scheme of whites and greys with a little flesh colored paint mixed in for the brightest highlights. A mix of Tamiya Clear Red and a flat red color (no ratio given, but I'd assume heavy on the clear) was used to color the monotone shade coat into the bright red of Saim-Hann.
What if you did something similar, leaving white for the brightest areas and grey to a darker grey (avoiding black) for the shadows and then come in with washes or Tamiya Clear Green and Blue? You could probably even do a zenithal spray with rattlecans of grey and white for the base and shading.
Edited by Brother Chaplain Kage, 10 July 2017 - 12:17 AM.