These biscuits can keep in an airtight container in a cool place for up to two weeks.
You can buy this in most supermarkets or make your own. Place white sugar into a jar with a tight fitting lid. Drip two drops of food colouring onto the sugar, close the lid and shake for about 1 minute. Adjust the colour with additional food colouring and repeat till you get the colour you want. Make sure the sugar is dry and there are no lumps before using.