Lightening hair help

Hi so I heard you can't lighten colored hair with color. My natural hair is black and I have been dying my hair a level 6A for a long time now. When the color fades I notice it being lighter than after I dye it. With my faded hair is it possible to lighten it with color? I was thinking of dyeing my hair a level 7A next time.

I would imagine that this would be possible.  Did you try it and how did it work out for you?