Lead Developer
Hi there,
The mobile nav button takes on your styling from the desktop navigation.
To change it, you can use the selector I shared here: https://generatepress.com/forums/topic/mobile-css/
Let me know if you need more info 🙂
Documentation: http://docs.generatepress.com/
Adding CSS: http://docs.generatepress.com/article/adding-css/
Ongoing Development: https://generatepress.com/ongoing-development