Nitrous Blue. It's a color exclusive to the Focus RS. I sell fords for a living and always feel if you're getting somthing special like an ST or premium Mustang why wouldny you get it in a color thats exclusive to that model?
For the Fiesta it molten orange, the Focus ST tangerine scream, the RS its nitrous blue or stealth and for mustangs triple yellow or competition orange.
If you're getting an ST fiesta why wpuld you pick a color that can be confused for a regular fiesta?