There shouldn't be any problem substituting. In fact, you may get a more robust flavor in your lamb! You might not want to do this in a dish where the color of the sauce is important, but in a case like this it should be fine. You also might want to consider using a lighter red wine, like a Merlot or Beaujolais, if you have them on hand instead of the white wine. That should keep the flavors closer to the original recipe, if that's important to you.