How to add visual effects on QGraphicsPixmapItem?

Question

I am using Qt 5.5.0.

I want to know a good way of adding (and removing) a simple effect on QGraphicsPixmapItem-s.

More specifically I have multiple QGraphicsPixmapItem-s moving on the scene. When they collide I want one item to turn white for a moment and then back to the original pixmap item.

Only thing I found in the docs for QGraphicsPixmapItem Class that could be what I need is the virtual void paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget) member. But how do I use it to achieve my goal?