Conditional formatting applies formatting depending upon a cell's value.
- Select the range you wish to format.
- Choose Formatting → Conditional Formatting.
- A cell can have, at most, three conditions.
- The conditions are evaluated until one is true. That condition's formatting is applied. Remaining conditions are not evaluated.
- Only one condition's formatting will apply to a cell--the results of multiple conditional formats are not "combined" in any way.