henna. green hair!

Hi. This is a helpful site, and thank you. I`ve been using Avigal Henna. I used brown to cover my curly hair, with red first to cover some grey strands. My hair is brown, past shoulder length. I had used the henna colors before, and this last time, about one and a half months ago, my hair turned out charcol with the grey strands not covered. Now it has faded to brown, and also has big parts that are a slightly darker brown-black color, with a green tint in the light. It`s not that obvious, except that in the light I feel like a plant! I thought that since red is the opposite of green, it might neutralize the green. I`m not sure what to do. Several of my students asked if my hair is green. Thank you for your help.