try {
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    System.out.println(UIManager.getColor("TableHeader.background"));
catch (Exception e) {
    e.printStackTrace();
}

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");

try {
        UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        System.out.println(UIManager.getColor("TableHeader.background"));
    } catch (Exception ex) {
        // HANDLE EXCEPTION
    }

try
{
    System.out.println(UIManager.getColor("TableHeader.background"));
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    System.out.println(UIManager.getColor("TableHeader.background"));
}
catch (Exception e) { e.printStackTrace(); }

javax.swing.plaf.ColorUIResource[r=238,g=238,b=238]
javax.swing.plaf.ColorUIResource[r=240,g=240,b=240]