Yeah, it depends on the scenario, green is like a very peaceful-ish color, red is like something to relate with urgency (In a negative way). Red in real life means danger, stop, error..etc.
I wanted to recommend red too initially, but I think for his use case blue or green would go well because of the background image (and also for the reasons above).
This guy does a nice job explaining how sometimes it's not so much the color, but how you use it. "What stands out gets clicked, what blends in gets ignored."