I do most of my work in Vim (or Neovim) in tmux inside of iTerm on my Mac.
I found my color schemes were being properly applied in Neovim but not in Vim (version 8).
Adding the following values to my
.vimrc corrected the problem for me.
let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum" let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"