Harness provides advanced support for blue-green deployment strategies on Amazon ECS, allowing for seamless updates and instant rollbacks with zero downtime. This is achieved through the use of Elastic Load Balancers (ELB) or Route 53 DNS updates, which enable businesses to test new versions without disrupting production traffic. Blue-green deployments involve two versions of an application: the "blue" version handles live production traffic, while the "green" version remains idle for testing. Once the new version passes verification tests, it can be rapidly swapped into production, with the flexibility to revert if necessary. Harness simplifies this process by managing listener rules and offering continuous verification using tools like Splunk and New Relic. This approach enhances operational efficiency and reduces deployment risks.