The status bar, is show information, about script compilation, and Force additional global background tasks.
Edit
For now status bar only change the color to orange when you run the runtime (play the game), and change the color when you run the simulation mode and show the build of the engine.
Simulation
When you play the game status bar color will be red.
Runtime
Also status bar will change color when no scene is loaded or when user create first project.
Empty Scene or Startup Window
Status bar show that script project is building
Status bar shows that project and its scene was saved