I went looking for info on one of the coolest colors I've ever seen. Polychromatic Grey. Imagine metallic flakes about that size, but equal parts red, blue and green. I saw it on a 1956 Buick (probably in the 1970s) but it turns out it's probably a Norton motorcycle color.
https://www.nortonownersclub.org/node/7129 The last comment suggests as an alternative
Platinum Grey Metallic over a gold base coat.