@Derrick-Hawkins ,
If you mean temporarily highlight (*), then select one of the column headings, then Search > Style One Token and pick one of the five available colors. If you have more than five columns, you can apply multiple colors to the same heading (with anything from 1 to 5 colors active at the same time on each, you can get 31 different combinations) (*: “temporarily”, because text files cannot save color information, so when you reload Notepad++, or open it on a different computer, it won’t have those colors saved; if you are looking for a word-processor-like feature where the text has that color permanently applied, then you need to find a word processor, not a text editor).
But since you’re working with tabular/columnar data: if your columns are comma-separated, then the CSV Lint plugin will help you automatically highlight columns; if your columns are separated by spaces/tabs, then you’ll definitely want to use the Columns++ plugin (though I don’t remember it having the header or full-column highlight, or just a gazillion other features which make column manipulation easier; the author @Coises can chime in at this point).