vim-monochrome works in GUI/true-color terminals, as well as 256-color terminals:
The status line in the screenshot is
lightline.vim with the nord color
scheme, which is a great match.
Installation depends on how you manage packages. For example, with vim-plug add
Plug 'fxn/vim-monochrome'
to your init file.
Just throw this to your ~/.vimrc:
colorscheme monochrome
Comments can optionally be rendered using italics:
let g:monochrome_italic_comments = 1
colorscheme monochrome
It is important that the flag is set before loading the theme.