In a medium saucepan (preferably nonstick for easier cleanup)
Whisk to combine the rice flour, wheat starch, and sugar.
Add the milk, oil, and food coloring until smooth.
Heat over medium heat.
Using a flexible spatula, continue to stir and scrape the sides and bottom of the pan until the batter transforms into a cohesive dough, (It should resemble Play-Doh) and pulls cleanly away from the sides, 3 to 4 minutes.
Transfer the dough to a work surface lightly dusted with wheat starch and allow to cool completely.
Dust the surface of the dough with a little wheat starch and knead until smooth, 1 minutes.
Divide the dough into six equal pieces with a bench scraper )for accuracy, weigh with a digital scale if you have one)
Roll the pieces into smooth balls and then flatten with your hands into 4-inch rounds. Continue to dust with wheat starch as needed.
Set the dough rounds on a plate and cover loosely with plastic wrap.
Refrigerate until cool to the touch, at least 30 minutes or up to 2 hours (any longer, it will be too firm to assemble) before filling the mooncakes.