From the pictures, it looks like it's a medium/dark blonde. It's not so light that it would go green or muddy with a medium brown, especially if you choose a warm brown which most box colours are. You can strand test to be sure.
There are some nice semi-permanent browns in Adore, box colour is very harsh on prelightened hair (looks like the ends are lightened) and you wouldn't have the damage if you use a semi.