If the other cell is CF - make the target cell respond to the same format conditions.
If it is not: too many things to consider to even start explaining. you can maybe get a condition evaluate to TRUE, but the Format for this conditions is already defined - and you have to change it. But then NO event is triggered upon coloring the other cell to tell you that you have to do so. All in all it's easier to just press a button to transfer the format from one cell to the other.
Or you have to find a suitable cell value to base your conditional formatting on.
IMHO you should reconsider the idea to use CF in this way - there probably easier ways.