I think it can be changed in Display Properties>Appearance>Advanced. Click
on Items and you see a list of all the things that can be changed. It's very
hazy as to which is for which. You have to try each to see what it affects.
Each have sizes, colors, and other things. I think it is one of these were I
put color on my task bar but it was a year or so ago when I did it and don't
remember specifically which.