But there is some logic in the use of colour as well. Clicking on the little colour squares also means a switch in the background colour here. Notice the deliberately minimal design aesthetic employed here. As you'd expect, Coke has a more complex site. The answer to the last question probably hinges on issue of text display.
Users typically prefer small text to appear black on a white background.
Beige is close enough. Balancing Function and Aesthetics I have spoken about two, typically conflicting, approaches towards web authoring. One approach argues for the relative positioning of elements on the web page, the other for absolute positioning. The latter tends to be adopted by design focused people. They like the idea of being able to control all the various design elements.