QT - how to change style of active QToolButton in menu?

Question

Qt

In general, there is a QActionGroup. There is a task - for the selected menu item to make the bottom frame thicker and with an arbitrary color. How to do this?
The code is something like this - there is a QActionGroup, QAction is added to it. You can get a QToolButton from a QAction, but how can you get it through the QAction's triggered signal?