In the bowl of a stand mixer, whip the heavy whipping cream on high speed with a whisk attachment until stiff peaks form, about 5-7 minutes. Fold in the sweetened condensed milk gently until fully incorporated.

Divide the cream mixture among four smaller bowls. Stir the Jello powder into each bowl (one bowl with raspberry, one bowl with orange, and so on).

Drop heaping 1/4 cups worth of each color into a 9" loaf pan, layering the colors on top of one another in random patterns, alternating colors so there aren't giant patches of one flavor. Repeat until bowls are empty. Use a butter knife to gently swirl the colors together a couple of times. Cover with plastic wrap and freeze for at least 8 hours, preferably overnight, before serving.