Hair indigo on cellophane?

I have very light brown hair that I recently dyed blue-black with semi-permanent hair color. I like the way it looked so I have decided to permanently dye it black with hair indigo. But I don't know how well it will take if all of the cellophane hasn't washed out. Can someone tell me if it would be alright for me to go ahead even though I still have a little color in my hair?