Divide white bean paste into 6 balls.
Using your hands, flatten a ball of shiroan and wrap it around a cube of mango. Repeat for all six pieces. If the mango is very juicy, the bean paste may get sticky. In that case, dust with katakuriko to keep it from sticking to your hands and dishes.
Set aside while you prepare the mochi.
Add shiratamako, sugar, water, and food coloring (if using) in a bowl. Mix to combine.
Transfer mochi batter to microwave safe bowl (I line my bowl with a damp washcloth) and cover well with plastic wrap, another dish, or other cover. Microwave for 2 minutes and 30 seconds.
Carefully dump cooked mochi onto a surface lightly dusted with katakuriko. Divide into six pieces. While you work with one piece, keep the others covered with a damp cloth so they don't dry out.
Flatten one piece (either with a small rolling pin or your hand), and place wrapped mango in the center.
Wrap the mochi around the mango ball, pinching the edges to seal them. Dust in katakuriko and you're done! Daifuku should be eaten the day they are made.