How set colour and background of tab chars?

How can I set the font colour and background of a tab character in Kate?

It seems that Kate might be the most convenient way of editing .tsv files.

(I think at some point I may have set some option to display tabs, but if I
did I can't remember now how I did it. All the same ....)

They display as chevrons >>. But it's hard to see them. I couldn't see any
such char defined in the settings>colours/etc dialog.

._.