You also have to remember that the X-Wings were all painted differently to help sell the idea of the rebel force being a rag-tag organization. The Red 3 model you linked to, to my eye, looks like it has a lot of weathered gray on it, rather than silver. I'll concede that it could look like a metalic if you squint and really want it to look like a metallic, but, due to the realities of how these things were photographed, metallics would not have been used.
Of course, if you like the idea, go for it. I think it'd be kinda cool to see.
--Alex