Dissolve each box of flavored gelatin in 1 cup boiling water in 4 separate bowls. Stir well.

Add 1 cup cold water to each bowl. Stir to combine.

Pour each gelatin mixture into separate sections of a 9x13-inch dish. Chill for 2 hours.

Combine milk and sugar in a large bowl. Stir until sugar dissolves.

Soften unflavored gelatin in 1/2 cup cold water for 1 minute.

Add softened gelatin to milk mixture. Stir well.

Pour sweetened condensed milk into milk mixture. Whisk until smooth.

Remove set flavored gelatin from the fridge. Cut into 1-inch cubes.

Pour milk mixture over gelatin cubes. Rearrange cubes if needed.

Chill for 2 hours until set.

Cut into squares or desired shapes and serve chilled.