I think I watched an episode or two of this back in the day. Let's see…
There's a green haired chick, and Lelouch's with his crazy eye. He's Zero? He's evil? He has a friend with brown hair who's British unlike him??? But still has a Japanese name? There's a girl with long brown hair, she's a princess. And they're in high school. There's like a class system because Japan is imperialized by England or something? And although it looks like Clamp the show totally isn't by Clamp? And for some reason there are mechas in this show???? Why are there mechas??? I'll stop now.
The green haired chick gave Lelouch his crazy eye. He is Zero. He is a vigilante. He has a friend who was the son of the Japanese Prime Minister and he's "redeeming" himself by becoming an honorary Brit. The girl with the long brown hair is an exiled princess. They are high school (you know mangas, they target people around those age so they set the characters' age with theirs). Not really a class system, but it's like they're oppressed or something, because England imperialized Japan. It is by Clamp, but it's a collaboration of some sorts with Sunrise (people who made Gundam, which explains the mecha).
It's a nice anime. You'll get the answers in the end, but you know Clamp. Sometimes their stories are so messed up.