Suppose you have weird taste and you absolutely want:
- your visual selection to always have a green background and black foreground,
- your active statusline to always have a white background and red foreground,
- your very own deep blue background.
Your first reflex is probably to put those lines somewhere in your vimrc:
highlight Visual cterm=NONE ctermbg=76 ctermfg=16 gui=NONE guibg=#5fd700 guifg=#000000
highlight StatusLine cterm=NONE ctermbg=231 ctermfg=160 gui=NONE guibg=#ffffff guifg=#d70000
highlight Normal cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
highlight NonText cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
But it quickly appears that those lines have no effect if you source a colorscheme later in your vimrc so you move them below:
colorscheme foobar
highlight Visual cterm=NONE ctermbg=76 ctermfg=16 gui=NONE guibg=#5fd700 guifg=#000000
highlight StatusLine cterm=NONE ctermbg=231 ctermfg=160 gui=NONE guibg=#ffffff guifg=#d70000
highlight Normal cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
highlight NonText cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
which gives the desired outcome. Everything is fine. In principle.
But you like to try new colorschemes, or you prefer to have different colorschemes for different filetypes or time of the day and your overrides don't carry over when you change your colorscheme.
This is because colorschemes usually reset all highlighting, including your own, when they are sourced.
The solution is to override the desired highlights in an autocommand that's executed whenever a colorscheme is sourced:
augroup MyColors
autocmd!
autocmd ColorScheme * highlight Visual cterm=NONE ctermbg=76 ctermfg=16 gui=NONE guibg=#5fd700 guifg=#000000
\ | highlight StatusLine cterm=NONE ctermbg=231 ctermfg=160 gui=NONE guibg=#ffffff guifg=#d70000
\ | highlight Normal cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
\ | highlight NonText cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
augroup END
colorscheme foobar
Note that the autocmd must be added before any colorscheme is sourced or it will have no effect.
Of course, we can go one step further and put all our highlights in a neat little function for maximum readability/managability/maintainability:
function! MyHighlights() abort
highlight Visual cterm=NONE ctermbg=76 ctermfg=16 gui=NONE guibg=#5fd700 guifg=#000000
highlight StatusLine cterm=NONE ctermbg=231 ctermfg=160 gui=NONE guibg=#ffffff guifg=#d70000
highlight Normal cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
highlight NonText cterm=NONE ctermbg=17 gui=NONE guibg=#00005f
endfunction
augroup MyColors
autocmd!
autocmd ColorScheme * call MyHighlights()
augroup END
colorscheme foobar
NOTE: The autocommands above use the glob * in order to override any colorscheme. If, say… you really like the colorscheme foobar but you can't stand its Visual highlight, you will want your autocommand to target that colorscheme specifically. To this end, you can use the name of that colorscheme instead of *:
autocommand ColorScheme foobar call MyHighlight()
NOTE: This won't work if you have an autocommand like the following in your vimrc because autocommands don't nest by default:
[...]
autocmd BufWritePost $MYVIMRC source $MYVIMRC
[...]
The solution is to add the nested keyword to that autocommand to allow other autocommands to be triggered by that event:
[...]
autocmd BufWritePost $MYVIMRC nested source $MYVIMRC
[...]