I'm restoring a 1988 bicycle that's in great shape overall. One part that's bothering me is that the brake and shift cable housings are white in color but appear a bit yellow due to the bike's age. The housings are physically in great shape, so I'm wondering if there's some technique to bring back the original white color rather than having to spend a bunch of money on new housings that aren't quite "period correct"? I'm guessing the answer is "no", but I also wouldn't be surprised if there's a whitening trick out there I just didn't know about.
The cable housing shown below doesn't look all that bad against the blue frame, but the top-tube of the bike is white and it's much more apparent that the rear brake cable that is runs across the top tube has yellowed and doesn't look so hot.