Procion fiber reactive dyes are for plant-based cellulose fibers such as cotton and flax/linen. They require an alkaline environment to bind to the fibers and develop the color properly. That said, I don't know that I would use them in soap making.
For one thing, you'd need to test to see if the color stays true in a very alkaline environment such as soap. Also fiber reactive dyes react with the fiber just like the name says. Excess dye is normally removed before a person would wear the dyed fiber. They're skin safe in that kind of situation.
I couldn't guess whether they would be skin safe in soap or any other situation where they aren't bound to cellulose. That's definitely an "off label" use for these dyes, so unless you figure this out for yourself or find another soap maker who has that knowledge, it would be swimming in uncharted waters.