From my limited knowledge of source lighting, it would seem to my eye that you haven't thinned your source lighting highlights enough.
It needs to be really thin and the highlights worked up in a (censored) ton of thin, translucent gradually brighter layers. How many layers? - No idea
Best of luck with the next go!
Source lighting is a bitch to pull off, but it looks like you've got the right idea, just need to go for a more subtle effect, and as many others have said - work with more layers of thinner paint.
I make no claims of being a particularly good painter, and all my attempts at source lighting have gone completely pear shaped (way worse than your example here) but it might also be worth trying it out with a different colour scheme while you're getting the hang of it. Green light cast onto red armour is going to be trickier to get looking right than say... Green light onto pale blue armour.
The first time I try any new technique I find it's best if I can find ways to make it as easy as possible for myself, and then work my way up to more challenging applications of the technique.
Thanks for that, guys. I'm going to red wash over the plating and try and start from scratch, thinning it down a bit more. Or maybe just try darkening the edges a bit. I'm not sure.
I've actually been putting off painting the source lighting on this model for about four days now just because I knew it was going to be hard and I was probably going to ruin what had been up until that point a really satisfying paint job. So when I started this morning, I rushed right in. Impatience cost me.
The other thing that bit me in the ass is actually trying to work out where the light has come from. If I'd started with an Auspex instead, it creates pretty much a cone shape straight out and getting the shape would have been easier. The damn pistol creates light in a 270 degree arc sideways and a 180 degree arc front to back. It's doing my head in.
I'll spend the rest of the day having another crack at it and re-post tonight.