Customising the colours of vim’s tab bar

You can do the following, for example:

:hi TabLineFill ctermfg=LightGreen ctermbg=DarkGreen
:hi TabLine ctermfg=Blue ctermbg=Yellow
:hi TabLineSel ctermfg=Red ctermbg=Yellow

This line affects the window counter per tab:

:hi Title ctermfg=LightBlue ctermbg=Magenta

Garish colours chosen to highlight what each of the items changes.

I find that looking at $VIMRUNTIME/colors/*.vim really helps when playing with highlighting.

Note that these change the colours for Vim running in a console. If you want to change the colours for GVim, you need to use guibg, guifg, et cetera. For example:

:hi TabLineFill guifg=LightGreen guibg=DarkGreen ctermfg=LightGreen ctermbg=DarkGreen