How do I change the colour of the statusline of the currently focused window?
I've seen colorschemes modify this. Is this some sort of highlight group? Or something else?
You can change it in your vimrc. The currently focused window is highlight group
Statusline, other windows are
Example for terminal Vim:
hi StatusLine ctermfg=8 ctermbg=2 cterm=NONE hi StatusLineNC ctermfg=2 ctermbg=8 cterm=NONE
For the GUI, use