.CSS replace item in menu using only custom.css in wordpress : I would like to replace this image when i scroll  down on another image .

1stly menu looks like : 
[![enter image description here][1]][1]


And when i scroll little bit down menu looks like : 
[![enter image description here][2]][2]
Is it possible to replace  using custom.css this item in menu? I just want to replace this picture on another picture. Is it possible to do by using only custom.css or i need to have acces to files and use here java? 
When it's possible can somene just tell how? 
Thank you.



  [1]: https://i.stack.imgur.com/eIRVC.png
  [2]: https://i.stack.imgur.com/zmEiw.png