I never did this, so I'm not quite sure about it, but I remember that my colleagues did it for the site we were developing, and it had the same minor problem.
I think you are on the right track, although the scroll properties should be in the css body as follows:
body { scrollbar-face-color:
Perhaps you could try specifying the desired text area and id property and apply this in css so that:
textarea.(insertrelevantID) { ..... }
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