@PeterJones said:

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).

There’s nothing in Columns++ for coloring text. The plugin is helpful if you want to do operations on data in visible columns (like right-justify the entries in a column, add the numbers in a column together, search/replace restricted to a column, do calculations to create a new column, sort on a column in situations that don’t work with Notepad++’s built-in sort) and/or to use elastic tab stops to make maintaining visible columns easier. It doesn’t do any coloring, though. Help is here if anyone wants to examine it to judge whether they might want to install Columns++.

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).