private static ColorUIResource getSystemColor( String name ) {
		Function<String, Color> systemColorGetter = FlatLaf.getSystemColorGetter();
		if( systemColorGetter == null )
			return null;

		// use containsKey() because value may be null
		if( systemColorCache != null && systemColorCache.containsKey( name ) )
			return systemColorCache.get( name );

		Color color = systemColorGetter.apply( name );
		ColorUIResource uiColor = (color != null) ? new ColorUIResource( color ) : null;

		if( systemColorCache != null )
			systemColorCache.put( name, uiColor );

		return uiColor;
	}
Syntax: systemColor(name[,defaultValue])
  - name: system color name
  - defaultValue: default color value used if system color is not available
flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java