The background color is one of my favorite blues ever, which I rarely use because the paint fades so badly. No clue what pigment it is, was some very old Grumbacher Academie tube that has long since been thrown away. Just one well in my palette remains, trotted out for special occasions that don’t require lightfastness. Other paints used are Raw Sienna/Burnt Sienna (PBr7), Ultramarine PB29 in the shadows on the shell, and PB60 for the ground shadow.
Switched tools and drew this with the Kuretake #40 brush pen, same Carbon ink as before. 8″ x 2.25″ approximately.