Select the cells you want to highlight
Go to the Home tab
Click Fill Color in the Font group
Choose a color
Use Conditional Formatting for automatic highlighting based on rules
Go to Home > Conditional Formatting
Select a rule type
Set the formatting color
Click OK
Use Find and Select to highlight cells with specific content
Go to Home > Find & Select > Find
Enter the value
Click Find All
Select the results and apply a fill color
Use keyboard shortcut Alt + H + H to open Fill Color
Use Format Painter to copy highlighting to other cells