module RubyXL::LegacyWorkbook

def modify_fill(style_index, rgb)
  xf = cell_xfs[style_index].dup
  new_fill = RubyXL::Fill.new(:pattern_fill => 
               RubyXL::PatternFill.new(:pattern_type => 'solid',
                                       :fg_color => RubyXL::Color.new(:rgb => rgb)))
  new_xf = register_new_fill(new_fill, xf)
  register_new_xf(new_xf, style_index)
end