private static Object parseColorSystemColor( String value, List<String> params, Function<String, String> resolver )
		throws IllegalArgumentException
	{
		if( params.size() < 1 )
			throw newMissingParametersException( value );

		ColorUIResource systemColor = getSystemColor( params.get( 0 ) );
		if( systemColor != null )
			return systemColor;

		String defaultValue = (params.size() > 1) ? params.get( 1 ) : "";
		if( defaultValue.equals( "null" ) || defaultValue.isEmpty() )
			return null;

		return parseColorOrFunction( resolver.apply( defaultValue ), resolver );
	}
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