I did a bit of research myself after reading about fake Dior lipsticks. I have got for free a plain blue plastic tube with Christian Dior instead of just Dior. This is usually the packaging for "gift with purchase" tubes. They dont bother to do the gold and black for the freebies. Also, I have purchased genuine Dior lipstick at Debenhams in the Middle East with the black and blue and gold tube with Christian Dior embossed on the tube.
I don't think its possible to fake or replicate the quality and unique fragrance of genuine Dior lipstick, so I say, go ahead and buy! Its unlikely you will be cheated.