@Pokoy I *finally* got around to testing your shader setup in a production context and it was really easy to work with. I wonder why you chose to use three separate Corona Color nodes rather than a gradient(?)
Sorry for the delay, only just remembered you answered...
This was the setup that made most sense to me in order to have different colors scattered randomly (by map). With a gradient you would need to either use UVs which can be problematic on some geometries or needs addtional work, or color them depending on viewing angle which is not what the effect is about imo since there's no thin film effect in play... Either way, happy you could use it.
I tried the OSL flakes shader the other day on a car paint material and unfortunately using OSL for normal maps seems to produce problems with normal shading in Corona, it's similar to the artifacts one gets with anisotropy or low-res geometry where faces start to appear and normals smoothing breaks. I'm not sure whether it's a general problem of Corona or if OSL shaders need some special care when used for normal map generation in Corona. It's a real bummer though since it really produces nice flakey reflections.