*Matcha & Food Coloring- The better quality your matcha is, the brighter green it will be. If color is really important to you in these cookies, make sure you have a vibrant green matcha, otherwise add a natural food dye in with your wet ingredients to get a brighter green.
** Royal Icing- Getting NATURAL grey-black icing can be difficult. Avoid adding too much charcoal, as it may affect the texture of your icing. You can leave out the charcoal and cocoa powder and color this icing any color you’d like. The cocoa powder helps darken this icing and is also gives it a yummy chocolate flavor.
Storage- Allow icing to dry fully before storing in a air tight container. Icing will get harder the longer is sits out. Cookies will keep in a container on the counter for up to a week
https://samcookskindness.com/diy-frankenstein-cookies-vegan-matcha-sugar-cookies/