A lot of people use formatting to denote important information in an Excel spreadsheet. In particular, they will use the color of a cell to designate a particular category. Pretty much all formatting information is lost when you import from Excel to R or any other statistical package. But rather than ask people to go back and fix things, there are a few tricks that you can use to recover this information, as is shown in this blog entry.
Neil Saunders. When life gives you coloured cells, make categories. What You’re Doing is Rather Desperate blog, August 4, 2014. Available in html format.