Bug#714414: Default colors for grub

[Joseph Carter]

This is what being stuck at home for weeks will cause—bug necromancy!

I disagree with Martin-Éric Racine that _no_ default should be applied at all, just that there ought to be means to change it, which might have some implications for #461851 complaining about the color choices used back in 2008. If they can be chosen in /etc/default/grub, then it doesn't really matter what the defaults are.

Joseph