Can I use dyed mulch in my run?

[kaddogmom]

We live in Pennsylvania and are new at this. Our chicks are only 3 weeks old and just finished building our coop and run. Our run is about 6 x 16 feet with a covered roof. I have left over black dyed mulch from our garden beds. Would it be ok to put this as a base in the run?

 

[rosemarythyme]

I personally wouldn't just because I'd wonder what exactly was in the dye, but I don't know for sure if it's actually harmful or not.