Divide white bean paste into 7 balls.
Using your hands, stuff each bean paste ball with a grape, smoothing the bean paste over the sides.
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 seven 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 grape/bean paste ball in the center.
Wrap the mochi around the ball, pinching the edges to seal them. Dust in katakuriko and you're done! Daifuku should be eaten the day they are made.