Strange... I mean this is the original sprite.
The post process and the PBR materials probably change the coloring slightly, but on my screen, Spaz has an orange belly and jaw.
As @Primpy said the bloom (and other post process effects) makes it slightly discolored, but it depends on the environment.

I made some comparison shots:

Left is emissive and unlit (so it can't recive light) and right is the material we use:


With a point light between them on the ground:


With a spotlight in front:


And just for laughs this is what spaz looks like when he is hit by a maximum brightness light:


(sorry for the low framerate)

Here is a pic of the raw Spaz material: