why is it that most popular casinos use a black and green color combination? Is there some kind of science or psychology behind it?
I'm not going to say there's a type of science or psychological shit going on, that probably gets influenced by those colours. It looks more like those are two bright colours on the spectrum -- you may be wondering how black fits into this explanation, but that's exactly what it is. The uniqueness also counts as an advantage to attract and keep people wondering -- "to what extent does these colors go, with an unlimited space and interface" ??
Does it actually attract more gamblers? just thought I’d throw the question out there, who knows, maybe one day I get lucky and open my own casino (daydreaming

).
Everything is possible, including owning yourself a casino later on. Infact, I'm beginning to think that you're building one so you just needed to confirm a color combination for it.