HighCharts: how to update bar color when updating the point value -

i use "update" command refresh value of point in series:

mychart.series[0].data[i].update(sigvalue); 

now update color of column/point well. tried

mychart.series[0].data[i].color = "#ff0000"; 

but did not work...

color should changed attr() function.

http://jsbin.com/ubapaz/10/edit

    $('#test').click(function() { chart.series[0].data[4].graphic.attr("fill","#ff0000");     }); 

api here reference.