public void setBackGroundColor(ColorRGBA bgColor) {
        if (!isInitialized()) {
            throw new IllegalStateException(
                    "The EnvironmentCamera is uninitialized.");
        }

        backGroundColor.set(bgColor);
        for (int i = 0; i < 6; ++i) {
            viewports[i].setBackgroundColor(bgColor);
        }
    }
Alter the background color of an initialized EnvironmentCamera.

@param bgColor the desired color (not null, unaffected, default is the
background color of the application's default viewport)
jme3-core/src/main/java/com/jme3/environment/EnvironmentCamera.java