I think a black Fiesta with a silver diffuser would like about as good as that Mondeo looks. If I had a black car, I'd paint the diffuser a very different shade of black from the car's color or an aluminum looking paint.
Here is a US spec Fiesta with the diffuser painted the same color as the body.
Personally, I am not a fan of that look. I think it'd have been far better if the diffuser section was black. I painted mine flat black and held the gun back farther to kinda texture it, then sprayed it with a satin clear. Didn't want that section to be glossy or smooth.