With this research in mind, we came to the realization that there was little consistency between this collection of maps and no real indication of a common “correct” palette for color and style rendering. By unifying and simplifying our own Google color palette down from hundreds to a small handful of colors, we were able to produce an experience that provided familiarity and uniformity as you browse the world. A sampling of our color palette studies and refinement.
To complement our new simplified color scheme, we created local variations to support familiar regional systems where needed (for example, the UK and Japan have more classifications of roadways than most of the world). In recent months we have introduced a few more regional changes to our color palette adding 3D building shadows to indicate local time-of-day. -via Google Maps: Designing the Modern Atlas - Core77.