Make a cell red/green if the value is positive/negative

How do you make a cell red/green if the value is positive or negative (gain loss) I have a metric i am tracking and i have the total % in the morning and the % in the evening. I need to track the % and make it easy to understand. So I want to make positive change green and negative change red i would be looking at change from morning to evening and change from evening to next morning. i am learning excel on my own so please forgive me if this is simple.
Thanks for your help in advance.

you would need to use conditional formating, select the cell/cells you want to format, then click on conditional formating -> new rule then go to "Format only cells that contain"

from there you can set your conditions and desired format. you can do a second rule for the negatives