Hi, @robberpen
You can refer to the online user guide for more details. The green debug button configures the debugger Settings, while the blue button automatically identifies and configures the debugger.
Run: When you create a run configuration, it is saved with the extension .launch in org.eclipse.debug.core. You can specify an alternate location in which to store your run configuration. You can also specify how you access it and what perspective to open when running an application.
Blue bugs are often used for debugging.
Best regards, Alex.
