Another explanation for color choices - the austere Jobs is no longer at the helm, it's Tim Cook, and Tim clearly wants to steer Apple into the fashion market - he recently hired many top execs from fashionable brands. Beats acquisition ties in as well - wearing Beats is more a fashion statement more than a technical selection.
There is a fine line between using things like color as a tool to shape a product, versus using them as an option to sell a product. I know which side Jobs was on.
