To mark some important fact, do you color cells in sheets? There is nothing wrong with that as long as you work with small datasets. But what if you have a table with thousands of records to browse through - a normal Excel user would start today. My students will not do that :-) and will use the command "conditional formatting", and Excel will search thousands of records for them and select the appropriate ones.
If you are trading in finance, or maybe you are an accountant or financiers, or maybe as an analyst, you must have swapped the negative values. In the balance sheet, it is customary to use parentheses instead of writing negative values. This article explains how to do it with custom formatting - CHECK
For some unspecified reason, the data.difference function is not automatically suggested. Especially for you, I present how to use it :-). Since it is a "ghost" function you will not find it anywhere - neither on the function list nor in the Excel documentation, and you have to enter it completely yourself.