ive seen that spoiler before, the word shopping trolley was used.
however, for me its simply a poorly executed concept - it just looks as though youve stuck one over another and not added to the overall design of the rear of the car.
the reason others have said that it would look fine if you contrast the two, such as matting one, is to try and visually make the spoiler blend more into the shape of the car, id rather the actual design of the spoiler do that.
i looked at very similar designs with my MK4, and ended up removing the original and buying an extended version of it that included side peices. that worked very well i think and was very noticable yet subtle at the same time