The Cart icon in the top right corner opens an overlay window for quick access to the Checkout and shopping cart pages:
You can edit its styles in the Header template > Menu Cart widget, as mentioned in this guide:
Lagar Elementor Theme: How to edit the Header section?
https://elementor.com/help/menu-cart-widget-pro/
However, the overlay window background colour is added to a global theme colour - Accent8. To access it, open the Elementor panel > Site settings > Global Colors > Accent 8
