I would just get them in whatever colour. I think custom / tinkered stuff looks cooler than shiny new stuff, but really nobody cares about what colour one of your binding's high-back is.
That being said, it doesn't really make sense that they can't replace the part with an identical part. Imagine if car warranties worked like that? "Yeah sorry we don't have any white bumpers left, but we have a whole bunch of yellow ones!"