Several things go into the process. First is to source large amounts of wood products. Next is your first grind through a mulching/grinding machine https://www.youtube.com/watch?v=p5cMv-L_Xgk
. Next is to let it sit and decompose for several months. During this time it is good to turn or agitate the material a few times to help with the process. After this decomposing process you then will grind the material again using a finer screen in the machine. After this and depending on the type of material being used you will then need to run it through a trommel screen http://www.youtube.com/watch?v=oA3SqbgwyJM
to get uniform material. After all this you can then add a dye or coal ash to color your mulch. The more popular colors would be natural, brown, red or black. I hope this helps, if nothing else I just bumped an old thread.