obsidian black
Iam sure they will love it. I use Prismacolor pencils for my coloring and use glitter gel pens for the accents.
Glitter pens I use:
http://www.amazon.com/Glitter-Pens-Best-Colored-Gelpen/dp/B00LPNJ8ZY
My coloring is not great or even close to what I see people on a facebook group that I am a part of. However, I just do it as a past time and for relaxation purposes.