Im not even interested in the xR as I have last years X that works wonderful. However, I remember this ad and seeing how visually appealing it was that we have a variety of choices here. It draws the eye, and had me considering a color despite me always going for black or gray in the end.
Now that the xR has debuted, they decided to add color but of course different than the standard rainbow colors.
I understand this is a much more expensive device. So with logistics and what not they probably studied colors for years before deciding on the current line up.
I just think it would have been cool to see and would have definitely brought on some impulse buyers.