Hi Rick,
1. Select the range of cells you want to colour code
2. Select Conditional Formatting from Home menu
3. Select Use Formula to ..... option
4. Enter =AND($N5>=0, $N5<>"") in the formula box
5. Click format
6. Choose your formatting
Done.
Repeat above for negative gains by using "=$N5<0"
Please do not take me wrong , but I think it would be better to ask these type of excel questions at the spreadsheet help forum, as this is not an STT matter. I do not mind answering if you tag me