Good question, I've heard a few different things. Imperial Blue is a soft pigment colour especially since these EU regulations came in with regards to water based paints.

I've seen some ST's and other Imperial Blues which look great, no marks whatsoever. I don't think the paint is different, just the shape of the car. The Focus is wide and has wider arches.

Most paint full stop is crap these days, I had a brand new Honda which the paint literally fell of with being water based.