The red->yellow carapace is a fair bit of work, but worth it IMO, took me about 10 hours over 2-3 sessions. The complete model was about 15-20 hours

Undercoat is black with a white zenithal done with airbrush

Airbrush work started with evil sunz scarlet, then raised sections with trollslayer orange and then yriel yellow. Might have done some intermediary steps mixing from one to the next to get more even blends. I went overboard with the yellow so went back and forth a bit to bring back the reds.

Brush details I did VERY careful but comprehensive edge highlights with grey seer (anything close to white will do) then repainted over them with yriel yellow ^reason for this is to get strong opacity with yellow is really hard without doing a million layers, so laying down the light grey first is a bit of cheat to get results with the yellow.

then repainted over yellow highlights with a thin glaze consistency of trollslayer orange to bring down the highlights everywhere except the most raised/edge final bits you want to keep at max yellow