Insertional inactivation of antibiotic markers is along and cumbersome process, because it requires simultaneous plating of two culture media. On the other hand chromogenic inactivation is a short method to distinguish between transformants and non transformants.

In chromogenic inactivation, the gene of interest is inserted in between the chromogenic gene.

Therefore, the recombinant DNA would not produce colour due to inactivation of the chromogenic gene. Conclusion:

Colonies producing colour are identified as non transformants whereas the colonies which do not produce colour are transformant colonies.