High contrast should be your most important goal when designing the screens. Since it's impossible to avoid that some of the time sunlight will be washing out your screen (unless you have a transflective screen), high contrast schemes will be at least partly visible. It looks like you mostly have that, except for maybe the unlock screen. Also, bigger is better. It's difficult to read small fonts when driving (and not very safe, either), so if you use words, use big fonts so they are easy to read. I think those two things are true for any installation. My own subjective judgement is that the scheme should fit with the look and feel of your car.