What it comes down to is marketing. A line of WSD bikes (or any new product) is a big investment for a company, market research and surveys of the target market probably led to the color choices. They're not going to invest a lot of money without doing at least some of this research. It's just not feasible to make bikes in every color somebody could possibly want, so they'll go with the color their studies show would be the most popular. My suggestion is to find a good frame painter and customize to your hearts content.
"Bicycling is a big part of the future. It has to be. There's something wrong with a society that drives a car to workout in a gym." -- Bill Nye