The Apple Blog has a nice write up on conditional formatting in Numbers.
The real power behind spreadsheets is not just how well they can crunch data, but how you can visually present the information in a variety of ways. Sometimes, however, you may want to give more attention to a particular area, or hide certain data if itâ€™s not relevant. You often see conditional formatting applied to financial spreadsheets where positive values are in black or green, but negative values are always in â€œthe red.â€ So how do you do that? Itâ€™s where conditional formatting, or formatting based on certain criteria, comes into play.