Bring a small pot of water to a boil. Once boiling, add the tapioca pearls and cook for about 5 minutes. Drain and transfer to a small bowl. Add one tablespoon of water to the bowl to prevent the tapioca pearls from sticking together.
Add the tapioca flour, rice flour, and sugar to a mixing bowl. Pour in the coconut milk and lime juice and whisk until well combined.
Transfer 1/3 of the batter to a small bowl and add a pinch of turmeric, whisk to combine. Add 1 drop of pandan extract to the 2/3 of the batter and whisk as well.
Bring a pot of water to a boil and place a bamboo steamer basket on top.
Slightly grease a 6-inch dish that can fit inside your bamboo steamer. I went with a round dish but a square one will work as well.
Give another good stir to your batters to make sure the tapioca flour hasn't set in the bottom. Pour a couple tablespoons of the green batter into the prepared dish, followed by a tablespoon of the yellow batter. Continue until no more batter remains and your have about 1/3-inch thickness. If using a small dish, steam in two batches. You don't want the batter to be higher than 1/3-inch, otherwise it will take longer to steam and you might not end up with an even texture.
Drain your tapioca pearls again and add them to the dish, distributing them evenly.
Transfer your dish to the bamboo steamer and steam for about 7 minutes, or until the batter is no longer liquid. It should still be tender and will firm up slightly as it cools.
Let it cool for at least 30 minutes. Flip your dish over a lightly oiled surface and cut into thick and long strips. The worms will be sticky so I recommend working with lightly oiled hands, it will prevent the worms from sticking to each other.
Enjoy as a snack! These sour worms are best eaten the same day but will keep for another day at room temperature in an airtight container.