What makes you think you can not already do this?
You can change the colour, line style and weight.
See Jon Peltier's page which explains
http://peltiertech.com/Excel/ChartsHowTo/ErrorBars.html
Cheers
Andy
> I would like to be able to customize error bars in MS Excel (change their
> color to match the color of the original chart).
[quoted text clipped - 7 lines]
>
> http://www.microsoft.com/office/community/en-us/default.mspx?mid=fb256c9d-7783-4
d44-90ea-807400d3b32b&dg=microsoft.public.excel.charting

Signature
Andy Pope, Microsoft MVP - Excel
http://www.andypope.info