It would depend on the quality of the two animals. If they are phenominal animals that complement each other then fine. But the odds of that are slim the darker the eb gene is seems the smaller/wedgier the animal. Color here is the last factor looked at when pairing up
That wouldn't be my first choice of a pairing, but if, like Kristy said, the animals are phenomenal and complement each other I'd have no problem with the pairing. Most people that do that combination though are going for the color and neglecting the quality of the chinchilla.