I hate it when plugins try to override my colorscheme, so I would highly discourage adding this to the plugin. To account for colorschemes that don't add color

I hate it when plugins try to override my colorscheme, so I would highly discourage adding this to the plugin. To account for colorschemes that don't add colors for SignColumn without angering users, use the `default` keyword without the bang. Some other things to consider: The sign column and line numbers are separated by the fold column. The default colorscheme has SignColumn and FoldColumn the same (Cyan or DarkBlue on Grey) and different from LineNr (Yellow or Brown).