You could also use whole butterflypea flowers or butterflypea tea: just steep in the warm milk for 10 - 15 minutes to impart the color, then strain and reheat with the spices and sweetener.
* Homemade blue food coloring from red cabbage (tutorial HERE) OR a small handful of butterflypea flowers steeped in 1/4 cup boiling water OR blue matcha powder ** You can use homemade coconut sprinkles instead, recipe HERE