In the bowl of a stand mixer, combine the gelatin and Sprite. Whisk to combine and let stand for 5 minutes. Meanwhile, bring a small pot of water to a boil. Place the bowl with your gelatin mixture over the hot water, and stir until melted.

Return bowl to mixer and fit with a paddle attachment. Combine gelatin mixture with about 2 cups of powdered sugar, and mix until it forms a sauce like consistency. Add in the salt, and continue adding powdered sugar 2 cups at a time, until a dough has formed. You may not use all 3 pounds of the sugar. Reserve excess for rolling out the dough later. The finished candy dough should be thick, malleable, and not overly sticky.

Turn the dough onto a surface dusted with powdered sugar. Using a knife, divide the dough into 4 portions. Place all the dough portions into zippered plastic bags.

Wearing plastic gloves, or between two sheets of plastic wrap, knead a few drops of food coloring into each portion of the dough until you have achieved the pastel colors of pink, yellow, green, and lavender. Knead well until the color is fully incorporated into the dough.

Have parchment lined cookie sheets ready. On a surface dusted lightly with powdered sugar, roll out the dough to 1/4 inch thickness. Use a small heart shaped cutter to stamp out the candy pieces. Reroll the scraps and continue cutting, until you have used all the dough. Transfer hearts to parchment lined cookie sheets.

Allow the cut-out hearts to air dry, uncovered, for 24 to 48 hours. Flip the hearts over about half way through the drying process. They should have a hard, crunchy texture.

After the candies are completely dry, you may write on the with food writing markers.

Store in an airtight container.