You can embellish your worksheets with borders, shading, and colors that are 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, 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.
If you're going to make the worksheets into slides for a presentation, you need to add bright colors and spiffy shading. Add borders, several colors, and a couple of patterns that do justice to your worksheet, but don't overwhelm it. Experiment with Excel's prefab AutoFormat table formats until you find the one that flatters your worksheet.