The color comes from using red or orange food coloring in either powdered or liquid form. Adding the coloring has no effect on the flavor so I chose to leave it out in this recipe. If you would like the chicken tikka to have a red or light orange color, feel free to add ¼ teaspoon of an orange-red food coloring powder such as the one from Busch’s brand or 1-2 drops of red or orange liquid food coloring.