But using black and red instead of green won't do any harm. The green background may do harm because it's inconsistent with the brand colours. The green colour doesn't seem to have been selected for any other reason other than it looks nice. It does indeed look well, but why not keep all marketing material on the same colour scheme.
Consistency is essential!
Every marketing campaign (no matter how small, even if it's only an ad for your Fantasy PL competition), should carry the brand colours, the brand crest/logo, and usually the brand motto. Look at Tesco, every ad will carry the same colour scheme of red, blue and white, it will bear their logo, and it usually has the "Every little helps" motto.
Brand colours are important. And i'd argue that when it comes to a football club, brand colours are even more important than they would be for Tesco or McDonalds.