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.
Working with large and very large data sets, you may find that an error will creep into your calculations. To avoid the tedious scanning of thousands of records for verification before sending a report or analysis to your supervisor, I will describe to you how you can avoid it. Do you know array formulas?
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