When I was delivering bread the bakery gave all us night shift workers day rated hi-viz shirts, but they were all yellow or green and they discoloured after one shift. The pink ones do discolour but they seem to not loose their hi-viz effect quite as quickly.
Night rated hi-viz, when we eventually got them, were better because they were red and blue with glo-tape and thread. The red and blue hid the dirt really well so it didn't look like we were delivering bread straight from a farm shed.
There has been studies done in the trucking industry here showing that people are becoming immune to yellow and green hi-viz. So many people are wearing them, including people that don't need to, they just become part of what your eyes expect to see and you will often overlook one making them not so safe at all.