Designers and artists know how to use lightness and darkness to draw the eye. Luxury vehicles, like the Range Rover, took note of this and got the two-tone trend rolling.
The problem for mass production vehicles was that the paint process behind producing a two-tone vehicle took time and added costs. Fortunately for us, new methods, such as FCA's wet-on-wet process, have been developed to speed things up.
There's also another reason why the two-tone paint finish has risen so rapidly with consumers. While White and black remain the most popular vehicle colors, they've started to decrease in popularity. By adding a secondary color, like the black roof to the white body on the RAV4 pictured here, they're able to create a much more robust design element that makes the vehicle pop.