The claim is that the greenish space makes dark objects appear more easily, and I know the “realism/fidelity” claims were clownishly wrong considering the space-fascist future features hand carts (that you have to buy with real world money!) and a star system loaded with 90s malls with hot dog stands, but something about making space itself a soupy greenish is… well… 
Superman 64 sucked, but at least it released as a complete product, didn’t cost .75 billion (and rising) to produce, and didn’t expect escalating sticker prices to play.