Sure, I can help you with that! You can use conditional formatting to achieve this. Here are the steps:

1. Select the cells that you want to format.
2. Go to the Home tab and click on Conditional Formatting.
3. Click on New Rule.
4. Select "Use a formula to determine which cells to format."
5. In the "Format values where this formula is true" field, enter the following formula:
   Formula:

   =A1<0 

   (assuming your data is in cell A1).
6. Click on the Format button and select the Font tab.
7. Choose the color red and click OK.
8. Click OK again to close the New Formatting Rule dialog box.
9. Repeat steps 3-8, but this time use the formula
   Formula:

   =A1=0 

   and choose the color green.

Now, any negative numbers in the selected cells will be displayed in red, and any positive numbers will be displayed in green. As the data changes, the formatting will update automatically.