You forger everything you have been taught so far and everything upside down (or rather inside out). You recesses will be the brightest part. Something like sunburst yellow, or even sunbusrt yellow+white.
The flat surface of plates will be the darkest, how dark it is up to you. I change it on mine - legs and arms are "colder" so I go all the way to black with light purplish wash the body is "hotter" so I stop at very dark red; it has to be red gore+some dark brown, possibly scorched brown, I am using Valejo and I use burned carmin for this. Alternatively you can stop at Violet-red , again Valejo has this color, for GW you have to experiment, probably a mix of some red with Liche purple.
How you blend in between is really depends on you. I go orange road, starting from fiery orange and slowly adding dark red to it brushing from the periphery to the center of the armor plates.
Anyway, I will post WIP of my avatar as soon as I nail down the color for his cuirass before I proceed to the head and the helmet.