Interlagos seems to only have the hint of purple in the shade? I saw a Z4M last week in the early AM and it looked very dark and had some purple to it, not very much like the majority of the pictures online.
Today I saw a Montego Blue Z4 and it looked like what I had expected Interlagos to look like, given most of the pictures online. I guess it's tough to compare without seeing in person, since most LCD monitors are wildly inaccurate with color, nevermind the cameras.
Personally, I think palladium/silver interior would go best with IB.