This example turns on up and down bars for chart group one in Chart1 and then sets their colors. The example should be run on a 2-D line chart containing two series that cross each other at one or more data points.
With Charts("Chart1").ChartGroups(1)
.HasUpDownBars = True
.DownBars.Interior.ColorIndex = 3
.UpBars.Interior.ColorIndex = 5
End With