Why is it that most popular casinos use a black and green color combination?
I might not have too many comments about casinos in a combination of black and green, yes the question that Op asked I had seen in one of the sources that stated.
The combination of black and green in casino design is often attributed to a blend of psychological effects and historical precedent. Green is associated with luck and prosperity, while black is seen as sophisticated and non-distracting, allowing players to focus on the games.
So if the OP wants to find out more, OP can see here about:
Casino Colors Psychology: Lucky Gambling Colors