If you know the trick, Word’s ‘Line Between’ option for multiple columns can be formatted to a different color or other types of line.
The downside Word’s standard line between column setting is the lack of formatting. There’s no known way to change the look of the vertical line between columns. Like the old Model T cars, your choice is black or black.
There are a few possible workarounds. We’ll be honest telling you there are downsides with the workarounds so we’ll explain the problems you might strike.
The most flexible one is changing the paragraph formatting to include a left-hand border to paragraphs on the right column (or right-border for the left column).
Do that from Borders and Shading | Borders | Options then increase the From text … Left (or right) so the line appears in the middle of the column.
Try a setting about 14pt and adjust to suit you. Too small and the vertical line isn’t centered between the columns. Too high and the line is cut off by the adjoining column.
You’re not limited to single block lines. The Style and Width options allow a wide choice of line styles and thickness.
More than two columns
This workaround also works for more than two columns. The same border formatting applies to all paragraphs from the second column onwards.
Now, to the problems with this fix.
Border settings work at the paragraph level. A paragraph split between two columns (like this example) adds the border line from the start of the paragraph not the top of the column.
The fix is to add a column break before a paragraph. Place the cursor at the start of a paragraph then choose Layout | Breaks | Page Breaks | Column
Adding a column break can mess up the balance of the columns, leaving white space at the bottom of a column. You might be exchanging one problem for another.
Needs constant manual adjustment
Because the border formatting isn’t linked to the column formatting, any change in the document is likely to mess up your line between / border formatting.
Adding more text, as in this example, pushed text to the column top.
Changing page size, margins, pagination and many other things could spoil the manual paragraph border formatting you set because Word rearranges the column wrapping.
If choosing this workaround, check that the border setting is correct immediately before printing or export to PDF.