I copied /etc/DIR_COLORS into ~/.dir_colors, modified it, login, but it 
has no effect.
I could not find any place where .dir_colors is evaluated in the 
init/profile scripts.

I had to add 

if [ -f ~/.dir_colors ]; then
        eval `dircolors --sh ~/.dir_colors`
fi

into .bash_profile to make it work

Maybe the right thing would be to do it in /etc/profile.d/colorsls.sh