3pcs White Food Coloring Markers, Edible Ink Pen with Upgraded Smooth Tip, Food Grade Markers For Cookie Decoration, Fondant,Cake,Frosting Decorating Supplies by Edibleink

Hi! A lot of the gray variations were wet on wet shading. The black lining was done with an Ateco black marker; the white highlights were done with markers very generically labeled as “Edible Ink Marker.” This is the Amazon link: https://a.co/d/0bGqZ7YB