Blue-white staining is a common technique using a reporter gene, lacZ which codes for Beta-galactosidase. LacZ breaks down a lactose analog which is provided in the growth plates as X-gal. This produces a blue colony. However, this process would be disrupted in the fragment of DNA is inserted into the plasmid. The white colonies have the lacZ gene disrupted. Through this method, the reporter gene can confirm the presence of the fragment.