If Blue-Green faild because of unexpected happens

[lcwxz1989]

if something unexpected happens with your new version on Green, you can immediately roll back to the last version by switching back to Blue

I think the question is not suitable in this project, if anyone know where is better, I appreciate your sharing.
I wander whether there are some best practices to do the data fix because of the unexpected happens, and migrate the fix data to old version database; or this are some other ways to do so(for example: product level, give users some coupons without fix the data or etc...)