I have few quetion about color scheme and terminals... The web is plenty of posts about it but I still does not understand the following:
After a fresh install of (g)vim on arch, I did a
$ vim new_file
then in vim I did
which result in several groups (the ones in :h highlight-default). More interestingly, they used colors that are not in my 16 terminals colors. I can see for instance
Folded ... ctermbg=82 ...
and the color shows the color number 82 of my terminal (confirmed with a printf "\033[48;5;82mTEST\n").
On the other side I have a minimal vimrc which only contain set t_CO=16 after the runtime! archlinux.vim. I also run vim inside urxvt-unicode where I put my funny 16 colors in the .Xressources. Also echo $TERM says "rxvt-unicode" without "-256color".
I don't understand why vim use these colors >=16 by default.