Add the cookies to the bowl of a food processor. Pulse until the cookies have been crushed into small crumbs. Transfer the crumbs to a bowl.

Dip a toothpick into green food coloring get and transfer a very small amount of the gel onto the crumbs. Repeat this process with the yellow food coloring, using slightly less than the green, if you wish for the moss to be a lighter green. Adding the yellow is optional. You can always add more color, but you cannot take it away.

Stir the gels into the crumbs with a small silicone spatula or spoon until evenly distributed. Add more color if desired. I wanted the moss to be a light green color, but you can go for a vibrant green moss or any shade of green that fits with your theme.