Lighten Your Hair with Lemon Juice

Does lemon juice work on medium brown or light brown hair? I heard that lemon doesn't work on colored hair. I colored it before with henna. It didn't make it red, thank god, it just gave me little orange highlights not the full-on orange.

I know that what colour I'll get differs from one to another, but what suggested colors can I mix it with conditioner then apply it on my hair? I want to get dark blonde. I know it will take a time, but how many times should I put it on my hair over 2 to 3 weeks? Is the change noticeable?

Nadine