Sorry.
Open you AdminCP, go to Styles -> Modify.
Click on [fonts/colors/etc] next to the style you want this to take effect on.
Look in the box entitled 'Head Insert', and find:
Code:
TEXTAREA, .bginput {
Underneath that, add:
Code:
border: 1px solid COLOR;
Click on 'Save changes' down the bottom and you're done.
Dave.
PS: You could be a little more polite to people who are trying to help you.
We don't get paid for it.