Here is my method of coloring cob pipes
For this cob mod I used Fiebings leather dye first one lighter shade of green and then a darker shade of green over that.
I scuffed off the factory finish that Missouri Meerschaum puts on their pipes with a scotch-brite pad. Before I applied the leather dye. I then use carnuba wax on the pipe to give the stain some protection and a bit of shiny look after buffing.
I also used a dark brown shade of Fiebings to color the bamboo shank.
I hope this info helps.