These colours are managed by dir_colors (man 5 dir_colors). The entry you are looking for is OTHER_WRITABLE (which is probably set to 34;42 at the moment).
Not all distro's come with a /etc/DIR_COLORS or ~/.dircolors, if you need to create one based on the defaults do this:
dircolors -p > ~/.dircolors
Edit the above file to your liking (colour-number combo's are explained in the man page and present in the .dircolors/DIR_COLORS file).