Is black-dyed mulch (bark dust) toxic?

My mother just had her beds re-mulched. They used black-dyed mulch, which is supposed to hold its color longer. It was recommended by the landscaping co. owner.

But the guy who actually led the landscaping crew today told her that the dye in this mulch is toxic, that it will kill her plants, and that she’ll need to have her beds completely dug up in a few years. (Why in the name of god this guy would be telling her this, after his boss sold it to her, I don’t know.)

So, my mother is completely panicked. Is she doomed? Are her plants poisoned? Or is the crew foreman full of it? (And yes, I know there’s not much to go on–the mulch could have been dyed with many, many things; I don’t know what the landscaper uses.)