Why do you say that? Apple has changed colors and added new ones before. Black turned to space gray, gold was introduced and when the C series came out there was a rainbow.
Gold was a new color, no different from white. They switched to Space Gray because of the anodization problems with Black and Slate. As much as I'd love for them to go back to all black, history is simply not on our side when it comes to them just mixing up colors for a change. Product Red sounds like a possibility though.