Prepare the fruit purees: Blend fresh strawberries with a little sugar until smooth for the red layer, and blend blueberries similarly for the blue layer. Transfer each puree to separate bowls and set aside.
Whip the heavy cream: Using a mixer, whip the chilled heavy cream with sugar and vanilla extract until soft peaks form, indicating a light and fluffy texture.
Divide the whipped cream into three equal portions. Gently fold the cotton candy or pre-whipped white cream into one portion to create a white layer. Keep one portion plain for the red layer.
Layer the mixture: Pour the red strawberry puree into the bottom of the loaf pan, spreading it evenly with a spatula. Follow with the white whipped cream mixture, smoothing the surface neatly.
Add the blue blueberry puree on top of the white layer, smoothing to create a vibrant, layered appearance. Cover the pan tightly with plastic wrap or a lid.
Freeze the layered mixture for at least 6 hours or until fully set. Once frozen, soften slightly before scooping for serving.