Any organic mulch benefits your plants. Shredded hardwood mulch does have bark, but if you mean the pine bark nuggets, those are ok as well. The shredded mulch will break down faster. Itis also less likely to wash away if you have any sloped areas and there is heavy rain. 

Mulch can also be leaves, pine needles, straw, and even shredded newspaper. 

Here are 2 articles on dyed mulch: 

• Is colored mulch bad for the environment? from Univ. of FL
• Colored Bark Mulch from Univ. of Mass Amherst

You don't want mulch touching the bark or base of plants because it can cause issues with girdling roots, insect or disease issues, and holds excessive moisture on the wood that can cause premature rotting. We have a blog post that you may find helpful about stem girdling roots and why those can cause tree health problems. It can also invite voles into garden beds since they like to tunnel just below the surface of the ground and chew on roots. This is more likely with shrubs like boxwood, cherry laurel, and rhododendron. 

Any mulch sourced locally is better for the environment since it is traveling less, plus it should be coming from landscape or yard waste instead of harvesting trees for the sole purpose of making shredded mulch. You can even get a free load of arborist wood chips delivered. This is more "green" and will take a little longer to break down, but it will still add nutrients to the soil. 

Perhaps you can give a monetary donation to the school if you would like to use a different mulch than what they are selling.    

Let us know if you have further questions. 

Emily