# File lib/bio/graphics/page.rb, line 206
      def add_track(args)
        #sort out the colour/gradient options
        [:fill_color, :exon_fill_color, :utr_fill_color].each do |colour_tag|
          if Glyph.gradients.include?(args[colour_tag])
            @svg.gradient(Glyph.gradient(args[colour_tag]))
            args[colour_tag] = "url(##{args[colour_tag]})"
          elsif args[colour_tag].instance_of?(Hash)
            @svg.gradient(args[colour_tag])
            args[colour_tag] = "url(##{args[colour_tag][:id]})"
          end
        end
        @tracks << Track.new(args)
        return @tracks.last
      end