The Styles Browser Background panel
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Styles also contain options for configuring the drawing area background, sky, and ground colors.
Use the Background button to select a background color for SketchUp's drawing area.
Use the Sky checkbox to have a sky color that is different from the background color. Use the Sky button to select a sky color.
Selecting the Ground checkbox selects a ground color that is different from the background color.
Slide the Transparency slider to adjust the level of transparency for the ground plane. Place the slider toward the left-most position to minimize below-ground visibility. Place the slider toward the right-most position to maximize below-ground visibility.
Show ground from below checkbox
Selecting the Show ground from below checkbox toggles the display of the ground plane from viewpoints below the horizon.