Hbar color - openflash chart

Rails
1

Hi, am using Openflashchart plugin,How can we change the color of each
bar in Hbar openflash chart

this is the code i have inside my controller

def stat_bar
title = Title.new(session[:tag])

hbar = HBar.new

hbar.values = [HBarValue.new(0,10),HBarValue.new(0,20)]
hbar.colour = '#FF8000' # this works for the two bars

chart = OpenFlashChart.new
chart.set_title(title)
chart.add_element(hbar)

x = XAxis.new
x.set_offset(false)
chart.set_x_axis(x)

y = YAxis.new
y.set_offset(true)
y.set_labels(["Yes","No"])
chart.set_y_axis(y)

render :text => chart.to_s

end

Please help !!