Using a 1/4 cup water, add in your red colouring and mix through. Then drop in peeled and diced (1cm cubes) water chestnut and let it sit for about 5 mins.
In a appropriate sized saucepan, add in the coconut milk, pandan leaves (in a knot), salt and sugar and bring to a simmer (not boil) and make sure the sugar has been dissolved. Let it chill down in the fridge to cold for service.
Bring another small saucepan to a raging boil, and add in your sago pearls and let it cook for approximately 4-5 mins or until the pearls almost translucent. Sieve through and run it under some water to chill it down to room temperature. Keep aside with a little water, so they don't stick.
Drain the water chestnuts, and with heat up 5 cups of water in a saucepan to a rolling boil, and cook through the sago for about 2 minutes. Drain and chill them to room temperature.
Coat them in the tapioca flour. And cook them in the boiling water again until the flour is cooked through. You can coat the chestnuts 2 or 3 times for desired thickness of the skin.
Finally, assembly time - the chestnuts and sago with the coconut broth can added into a appropriate serving bowl.