Steam sweet potato and yam for 5 minutes till cooked.
Syrup: Put grated coconut in muslin bag and squeeze out about 50ml coconut milk (a). Add 180ml water to grated coconut then squeeze out 180ml coconut milk (b).
Boil pandan leaves and sugar in 75ml water for 10 minutes. Allow pandan juice to cool then strain into bowl. Set aside.
Boil pandan juice with coconut milk (b), stirring constantly. Pour in coconut milk (a) and stir in salt. Remove from heat and stir occasionally to prevent curding.
Sago dough: Sift sago flour into large bowl. Stir in boiling water. Knead over lightly floured table to form smooth, fine dough. Divide into desired number of portions, then evenly blend a different color into each portion (omit food coloring for some if you like).
Roll out each portion of dough then cut into small pieces. Boil in water, stirring constantly till they float to surface. Remove and refresh in cold water for at least 5 minutes.
Drain and transfer to bowl. Sprinkle with 2 tbsp sugar to prevent lumping.
Place 1 tbsp each of sweet potatoes, yam and sago dough in bowls. Pour in syrup. Serve hot or cold.