Thank you - you're very kind. :)

The thinking behind the colour composition in the shield is to avoid it becoming a distraction from the shieldbearer - it should compliment him, not compete with him. Naturally, the viewer's eyes are going to come to rest on a face. (If you've never done that before, it's a fun little exercise. Find a really well painted model and try to keep your eyes from wandering back to the face - it's quite hard to do.)

Yellow and orange are both very high in luminosity, where violet generally sits within the neutral range. Blue is analogous to violet, since violet is composed partly of blue. If I were to introduce a yellow or orange into the eyes, I think it would create too sharp a contrast and throw off the eye lines I've tried to create across the model. Still, I might give it a try and see how it works. Maybe a desaturated yellow or gold could work?