In a large mixing bowl, whisk together the heavy cream, sweetened condensed milk, and vanilla extract until well combined and slightly thickened.

Divide the mixture into two separate bowls. In the first bowl, add the blue food coloring and mix until you achieve your desired shade. In the second bowl, add the green food coloring and mix until well combined.

In a freezer-safe container, layer the blue and green ice cream mixtures alternately, creating a swirled effect. Use a knife or skewer to gently swirl the colors together for a marbled look.

Sprinkle the crushed graham crackers, mini marshmallows, and rainbow sprinkles on top of the ice cream mixture.

Cover the container with a lid or plastic wrap and freeze for at least 4 hours or until firm.

Scoop and serve the mermaid ice cream in bowls or cones, and enjoy the colorful treat!