RDS Blue/Green wizard error: The current parameter group associated with the blue instance is not the default

Dear AWS Customer.

Thank you for your question.

The error that you got while trying to upgrade using Blue Green deoployment is caused due to the limitation which comes with blue green deployment- if the source database is associated with a custom option group, you can't specify a major version upgrade when you create the blue/green deployment.

As per the Blue/Green Deployment limitations for RDS MySQL (also applicable to MariaDB):

•	Limitation:

If the source database is associated with a custom option group, a major version upgrade cannot be specified during the creation of a Blue/Green deployment.

In order to resolve the issue with limitation you can follow the steps below:

1. Initiate the Blue/Green deployment, selecting the existing version of the database. Again, do not select a version upgrade, you will do this later.
2. Complete the Blue/Green deployment initialization until status is available for all resources.
3. Now perform and in-place upgrade to the Green database instance, selecting your desired engine, and associating parameter and option groups.
4. Continue evaluating and testing your Green database and proceed with the Blue/Green deployment process.

For more information, refer to [+] https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/blue-green-deployments-considerations.html