Originally Posted by Salamandrine

The Mercian pearl is definitely metallic. It's a pretty typical metallic looking finish, about like car paint. It isn't big flake 70s metallic or anything.

I haven't seen the polychromatic, but it sounds by their description like it is simply a very small flake metallic. I have seen this in 60s bikes. It doesn't really look metallic until you look at it very closely. It would make more sense if they called the polychromatic "pearl" and called the pearl "metallic", but it's probably an old shop tradition or something.