You can embellish your worksheets with borders, shading, and colors that can be cool, elegant, or professional. Your choice of formatting depends on your mood and the data inside the border. Sometimes a worksheet needs to be decorated to grab the reader's attention.
Always keep your audience in mind when you design a worksheet. If you're giving the worksheet to the comptroller of your company, then you might want to make it more reserved and subtle. You could add thick line borders to point out the bottom-line figures at a glance. Or you could add gray shading to the important numbers on the worksheet. Keep it simple, and you can't go wrong.