module RubyXL::WorkbookConvenienceMethods

def modify_fill(style_index, rgb)
  xf = cell_xfs[style_index || 0].dup
  new_fill = RubyXL::Fill.new(:pattern_fill =>
                                               RubyXL::PatternFill.new(:pattern_type => 'solid',
                                                                       :fg_color     => RubyXL::Color.new(:rgb => rgb)))
  register_new_xf(register_new_fill(new_fill, xf))
end