You know what, I totally botched up the names. It's not Interlagos, it's Ultramarine. Interlagos is a different color.
Ultramarine is the color they were going to release with the E90, and instead decided to save for the E92. Internally called Ultramarine, but renamed Montego. My bad.
Here's a link to GregA's post:
It's the color that was internally named Ultramarine Blue (Ultramarinblau). Montego Blue is a marketing name for that color.