Here is my analytical explaination I have given before in this newsgroup:
In classic mode you can change the color, thats easy. But if you want aero
then
see the below:
the themes are based on msstyles.. that color you are seeing is
actually a bitmap embedded inside the msstyle file and within vista you
cannot change it.. you cannot change it because that would mean that
you would need to extract the bitmap change its color and rebuild the
msstyle.
a non free option is to get the trial of windowblinds (stardock) and
after the trial pay 20 dollars
you can try the trial now and find hundreds of themes on
www.wincustomize.com but this also means you would need to use a compleatly
different theme,
or learn to use a tool that stardock has, to change the vista theme (yes its
possible)
HOWEVER there is a FREE way to change it theoretically
but I did not mention this because all these solutions DO NOT WORK with
SP1 that is just around the corner
but just so you will have an eye open for a new version here is the
info
A program that unlocks the ability for Vista to use 3rd party themes is
called vistaglazz
and then you can find other themes at
www.deviantart.com
or learn to edit the theme yourself...