Change QGIS Plugin theme to grey

Question

I am designing a QGIS plugin. I am struggling to make the outer region of the UI to be grey (see image).

The QT file is:

A reference UI that I want to make my UI look like, all non-functional space is grey:

Answer 1

You simply need to add a stylesheet to your plugin. Right click on your widget and select 'Change stylesheet'. Add this stylesheet for turning your QTabWidget to grey.

QTabWidget {
    border: 0px transparent black;

}

QTabWidget::pane {
    border: 1px solid #76797C;
    padding: 5px;
    margin: 0px;
    background-color: #D3D3D3;
}