I can't believe I never noticed this before…
I've had that G5 for almost a month and it has only just occurred to me that it has a bojacked handle. The front part and the grip at the top are correct, but the back panel has been replaced. Instead of being the proper 'cabernet' color, it's graphite gray from G4. the reason it didn't register with me is that it looks okay; in fact, it looks quite nice where the gray back panel wraps under the bottom to meet the burgundy G5 decal on the front of the handle.
I thought at first it might be an early G5 and they were just using up some random G4 parts, but the serial number suggests it was built in December 1997. putting it almost square in the middle of the G5's run.
Sure, I could spend a few extra dollars to replace it with one of the correct color, but what's the point? It looks just fine except for its mismatched cord hooks and I can live with that.