What happens if it equals 0?
If you want to continue for values equal to 0,
=IF(A1>0,"Stop","Continue")
If you need them seperated:
=IF(A1>0, "Stop",IF(A1<0,"Continue"))
Then go to Format - Conditional Format
Set the pattern to red if cell value equals "Stop"
Add condition
Set pattern to green if cell value equals "Continue"