Do you mean black/yellow? If the colors are right you should have a solid yellow and a black/yellow.
The black/yellow, unfortunately is not only hooked to the alternator, but is the wire that supplies the power to the fuse box. If that's the wire you mean, you've only islolated down to 80% of the car.
If you always do what you've always done,
You'll always get what you've always got