I went ahead and riveted the crest to the helm, and then antiqued it all black. The purple and red now remain only as highlights, just the look I was after.
I've been building the luminiferous aether collection devices that fit into the neckguard trim, and I can't assemble that until they are all cast.
Meanwhile, I have started on the headlamp. Here is a photo of the lamp as I found it at a yard sale. I will break it apart, and then the lamp will attach to the front of the helm.