Many terminals can display coloured undercurls that are different to the current text colour if that's what you mean. E.g. here's a plugin for simple-term to a

Many terminals can display coloured undercurls that are different to the current text colour if that's what you mean. E.g. here's a plugin for simple-term to add support for it: https://github.com/hexoctal/st-undercurl https://github.com/hexoctal/st-undercurl The Kitty terminal has all kinds of graphics addons including coloured undercurls and images too: https://sw.kovidgoyal.net/kitty/underlines/ https://sw.kovidgoyal.net/kitty/underlines/ Vim and NeoVim both support coloured undercurls too.