I love how you brought up split and steal because it's just a classic prisoner's dilemma problem. However, a difference between the split and steal TV show and this scenario is that they're going to meet each other irl again and it's done in front of a class. A chocolate quite frankly isn't big prize money so each girl is trying to look innocent and trustworthy in front of the entire class since chances are high they're in their social circle and they have accumulated social capital within the school already. Thus the right move is to play black no matter the result due to the stakes outside the game.
If you're a guy though, then the stakes outside change. Guys are generally rewarded socially as Varoon mentioned for NYC for being ballzy and ruthless. They're more likely to play red.
Take a look at this split and steal though: https://www.youtube.com/watch?v=S0qjK3TWZE8 It's very smart what that guy did. He psychologically forced the other player into a box by asserting that he'll play red, so that the other player will choose black since he's not gonna get a payoff either way.
As per your question, it's a basic game theory problem. If the conditions are set up in such a way that playing red is profitable even in the long term, then that's what you do. But that would involve a reason. As per playing red for no reason at all, it's a good strategy if you didn't know the risk of playing black was high and you just decided to yolo and screw someone over. But that's pretty much luck-based. Without any trigger to play red (such as an external job offer from a competitor paying 50% more or something like that, or new bad information about someone you're playing black with), that's the only way I see you can benefit from playing red, just dumb luck that maybe the person you're playing black with was planning to play red on you soon.