I have column B with different values on different rows and I want to set a rule that , for example cell b3 turns red if the value is smaller than that of B2 and green if it's bigger.
I know I need to use conditional formatting, but not sure how?

I tried the solution here (https://webapps.stackexchange.com/questions/88335/how-to-conditional-format-in-google-sheets-based-on-cell-directly-above-it) but that didn't work.

So what I want to say is: "if the cell's value is lower than that of the cell above it, color red, if the cell value is higher than that of the cell above it, color green".