It said a black back, not a black pastel.
I would keep the female and just buy a nice dom or co-dom male, or sell her out right and buy a nice male. How much does she weight, and how long have you had her? If she is a healthy, breeding size female, you can get more than $100 for her. You can also probably find a breeder locally who would be willing to trade a nice pastel male or something for another healthy, breedable female.