For the raspberry layer: Blend raspberries until smooth, strain out seeds. Whisk in sugar until dissolved, then stir in milk and lemon juice. Chill for 1 hour.

For the orange layer: Whisk together fresh orange juice, orange zest, and sugar until dissolved. Stir in milk and lemon juice. Chill for 1 hour.

For the lime layer: Whisk together fresh lime juice, lime zest, water, and sugar until dissolved. Stir in milk and optional food coloring. Chill for 1 hour.

Process each flavored base individually in an ice cream maker according to manufacturer instructions until soft-serve consistency.

No-churn option: Place bases in shallow pans in the freezer. Scrape vigorously with a fork every 30-45 minutes for 3-4 hours until slushy and thick.

In a large freezer-safe loaf pan, drop alternating spoonfuls of the raspberry, orange, and lime mixtures to create a checkerboard pattern.

Use a butter knife to gently swirl the colors together in a figure-eight motion. Do not overmix.

Press parchment paper directly onto the surface of the sherbet and freeze for at least 4 hours or overnight until firm. Scoop and serve.