In an all-grey conflict, neither side is totally good or completely evil. Both sides have a strong, justifiable reason for fighting, and contain a mixture of people of all kinds, from admirable, upstanding individuals to vicious, slimy scumbags. In most cases, one side has better reasons and more good people than the other. The protagonists usually fight for this better side, and if they don't, they'll switch sides before the end. While the audience roots for the better side, they still have sympathy for the opposition. Note that the sides often will still be Dress-Coded for Your Convenience.