Better color schemes

The game is pretty overwhelming visually. Map elements need more careful thought, especially zoomed in. It'd be quite useful to distinguish road type (the 3 colors zoomed out) also when zoomed in. There's a prototype in the `sam_colors` branch and various Google docs. It's also important to be friendly for various types of colorblindness. And there are some ideas floating around for different moods -- night, rain, autumn.

If anyone's particularly into colors, there are various google docs floating around I can dig up with notes.