Edible Spray Paint. So many times I've been making vegan cupcakes for some annoying vegan friend, and I've thought to myself, how can I stencil "EAT SUM MEET" on the top of them. This answers my prayers.
Metallic spray paint seems easier to find than other colors, but many craft and specialty baking stores carry the full rainbow. Or have it shipped from the UK, where Surbiton Art will supply you with a can of joy for about 20 bucks. Basquiat it up every which way, and bring your favorite person a gift basket of blue apples or silver tuna tartar or some other [color] + [food noun]. Theme parties and gift-giving cred will never be the same!
The Interblag also suggests using it as a way to "turn your body into a canvas of pleasure" C-3P0 Fetish shout-out.
[Image from CVXN]