Don't worry! I just personally don't really like green, completely personal opinion! Don't change it, as I suppose a LOT of other people love it the way it is.
Also I didn't say by any means that it looks bad. Still looks incredibly good!
And true the green is really necessary for the "zombie aspect" so overall the zombie part is perfectly executed.
PS: Didn't quite realize that this theme is also done with a premise. So of course the green is important for the zomie part. Keep it up