Google-sheets – How to apply formatting to another cell based on whether another cell’s date has passed or not

Google Sheets could be expanded to implement "a formula approach" for certain tasks. This is called "custom functions".

Custom functions should only be used to display values, so they should not be used to set the conditional formating directly. Instead use the conditional formatting built-in feature.

References

• Custom Functions in Google Sheets - Apps Script Guides
• Apply conditional formatting rules - Docs editors Help

Here is what you can do:

1. RightClick B2 → select Conditional formatting → select Custom Formula is (from the List)
2. Enter the following formula in the textbox: =b2>=c2
3. Check the Background Color and select green color
4. Click on Add another rule
5. Select Custom Formula is (from the List)
6. Enter the following formula in the textbox: =b2<c2
7. Check the Background Color and select red color
8. Click on Save Rules
9. Highlight B2 and click on Paint Format option on the tool bar.
10. Now click on cell B3 and drag until cell - B117 (this should apply the conditional formatting on cell ranging from B3-B117)

And for your second condition (i.e., to highlight D with green if it is greater than or equal to E, red if it is less than E) - simply repeat the above steps by interchanging D2 for B2 and E2 for C2.