I've never been a huge fan of the whole good/evil dichotomy myself, since it's far too rigid for what is inherently a chaotic system. I'm also a lifelong pagan, so the whole angel/devil thing is more amusing than anything else, right up there with original sin and purgatory (although Dante had a blast with it).
However, fire does not need to be crimson to be hot. You can have the white-hot flame of angelic justice, you can have the purifying fire of the heavens. It's your world, and your rules. Armor is much the same, and I like Melrick's idea of glass or crystal rather than metal, but if metal is your thing, how about electrum?