We used it on our tomato bed and it didn't have any adverse effects. It does fade a bit and if it gets disturbed and dirt comes out from underneath (my cats liked our tomato bed as a cat box) it looks a bit odd color wise. Unless you have black dirt:)

Supposedly the dyes they use are innocuous, but that is what many chemical manufacturers have said about their products too. In New Hampshire there are lots of trees that annually provide large volumes of material that can be used for mulching, at a very low cost. Why spend money on a mulching material is there is, better, material available essentially for free?