When you select a single cell, the cell is highlighted with a colored border. When you select a range of cells, the range is highlighted with a colored border and all cells except the active cell are highlighted with a colored fill. System settings determine the highlight color, but if selected cells are not clearly visible, you can change to a color that provides more contrast.
Important: Changing the system settings will affect the appearance of all selections in all applications. For example, the new highlight color will indicate selected text in Microsoft Word or folders that are open in the Finder.
On the Apple menu, click System Preferences.
Under Personal, click Appearance.
On the Highlight color pop-up menu, click the color that you want.
Note: You must close and then reopen Excel to see the new highlight color.