There is something wrong with how you've calibrated your monitor. Either that, or you're viewing the images on a bright white background. Do you play many computer games? These often start out by asking you to calibrate the gamma level of the game. Do you find that you often have to turn this way up to see the logos you're supposed to see in these calibration tools? I assure you, my monitor is ideally calibrated to do the kind of graphical work I need to for this game.
I do in fact use actual movie techniques for lighting night scenes. They are all brightly lit (some, like the Samarra and Nell sleep scene, contain light sources that are much brighter than those I use for daytime scenes), with a focus on outlines wherever possible (keeping in mind that the moving camera means that the light won't look ideal in every situation). I use special camera lenses to simulate the effects of low-light conditions, such as dulled shadows and a shift in white levels, without actually having to render true darkness.
What I don't want these scenes to look like, is the typical "night" you see in video games, where everything basically just looks like you're outside on a cloudy day. I want detail to be harder to perceive and shadows to be deeper and more mysterious. I want the player to fiddle around with the girls during the sleep scenes and grow in their anticipation of seeing them in full daylight because they can't really see the colors and details they might want to during the night.