Yellow food coloring
Combine sugar and water in a pan and bring to a boil. Boil for 1 minute and immediately reduce heat. Simmer for 1 hour or until thickened. Remove from heat and cool. Pour sugar-water syrup into a sterilized quart-size bottle. Add anise extract, vanilla, and food coloring. Stir gently and add the vodka. Cover and let the mixture sit for 10 days to 2 weeks before serving.