One of the teachers at my campus very kindly tested the olive dyeing for me. She had it exposed to UV light for 80 hours (it was supposed to be 60 hours but the technician did it for 80).
The fabric did fade and turned brown rather than the purplish colour that I had gained.
I am not too disappointed, it did dye, the brown is not awful and 80 hours is a fairly long time. It actually looks a bit like when I dyed it with alum. (The faded part is on the left.)