All the cells of negative numbers will become red, while the positive numbers will remain the same. You can create your own custom format in Excel to highlight negative numbers. Select the range ...

Instead, you might want Excel to display negative values in red, or with parentheses, or both. Microsoft Excel provides two ways to do so: a format and a conditional format.

Manage the display of positive and negative numbers with Microsoft Excel numeric formatting.

You can subtract numbers in Microsoft Excel in a few different ways, depending on your data and formatting.