Change side bar background color

how can i change the background of the navigation menu

Solution

You need to create a custom theme like this : https://filamentphp.com/docs/3.x/panels/themes#creating-a-custom-theme
This will create a css file in your /resources/css/filament directory (named theme.css for your panel). And next you can add your customized class on it, like :

.fi-sidebar {
    @apply !bg-gray-500;

    .fi-sidebar-header {
      //...
    }

    //...
}

.fi-sidebar {
    @apply !bg-gray-500;

    .fi-sidebar-header {
      //...
    }

    //...
}

dont forget run npm or yarn build / dev