Cleaning Black Stockings

So I started a new job last week.

Part of my attire included a new pair of Denier 50, and 40 winter stockings. It was soaked in a solution of laundry powder, and warm water.

An hour later, I was surprised to see the post soak solution thoroughly a dark pasty colour.

Me: It looks really pasty.
Flatmate: How long have you used it?
Me: Only this week.
R:Then it must be the dye.
Me: Dye??? I didn't think they dyed stockings...