Alert System

I want to have like an alert system for example like when i press the quit button it comes up with like a widget where it says like are you sure you want to quit and on that widget i want the background to be blurred but not the newly opened widget. Please help.

Add an image with a black color and set the transparency (Alpha) 0.8%.
That will make the background darker or use a white color and set the transparency (Alpha) to 0.8%.
tell me if you need more help.