Changing the Background Color

Relevant official examples: clear_color.

Use the ClearColor resource to choose the default background color. This color will be used as the default for all cameras, unless overriden.

Note that the window will be black if no cameras exist. You must spawn at least one camera.

fn setup(
    mut commands: Commands,
) {
    // this camera will use the default color
    commands.spawn(Camera2dBundle::default());
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        // set the global default clear color
        .insert_resource(ClearColor(Color::rgb(0.9, 0.3, 0.6)))
        .add_systems(Startup, setup)
        .run();
}

To override the default and use a different color for a specific camera, you can set it using the Camera component.

use bevy::render::camera::ClearColorConfig;

// configure the background color (if any), for a specific camera (3D)
commands.spawn(Camera3dBundle {
    camera: Camera {
        // clear the whole viewport with the given color
        clear_color: ClearColorConfig::Custom(Color::rgb(0.8, 0.4, 0.2)),
        ..Default::default()
    },
    ..Default::default()
});

// configure the background color (if any), for a specific camera (2D)
commands.spawn(Camera2dBundle {
    camera: Camera {
        // disable clearing completely (pixels stay as they are)
        // (preserves output from previous frame or camera/pass)
        clear_color: ClearColorConfig::None,
        ..Default::default()
    },
    ..Default::default()
});

All of these locations (the components on specific cameras, the global default resource) can be mutated at runtime, and bevy will use your new color. Changing the default color using the resource will apply the new color to all existing cameras that do not specify a custom color, not just newly-spawned cameras.