What is the difference between blue/green and red/black deployments?

Blue/green and red/black deployment strategies are often used interchangeably to describe a method of deploying new versions of a centralized application, where two environments run side by side to facilitate seamless traffic switching with minimal downtime. Although there are claims of differences between these strategies—such as whether both versions receive traffic simultaneously or not—tools like Netflix's Spinnaker, Kubernetes, and Istio treat them as synonymous, emphasizing that any distinctions are generally inconsistent and context-specific. Ultimately, these terms are used to describe the same overarching strategy of ensuring that a newly deployed application version is stable and tested before it receives all production traffic, though technical nuances might vary between specific implementations or organizations.