Red.
I recently saw a Zentangle tile that someone in a Facebook group had drawn in red. That was the first time that I‘ve seen a completely red tile. I thought it would be an interesting challenge to try my own. Shading with regular pencil looks a little strange, so I decided to try a red colored pencil. I chose a color that was a bit darker, and I think it worked very well.
On the other hand, I really don‘t like the corners with the Purks where I made them with orange beads. I think I should have just left it alone!
Zentangle drawn on Strathmore Bristol Vellum tile using a red, Micron pen. Shading and coloring done with Faber Polychromos colored pencils. White highlights made with a white Pilot Juice Up 04 pen.