Prepare the blue layer

• Blend the blue Jello, one envelope of unflavored gelatin and boiling water until the gelatin is dissolved.
• Stir in the edible glitter if using.
• Pour the blue mixture into a lightly greased 9×13-inch pan and let it set.

Prepare the red mixture

• Blend the red Jello, one envelope of unflavored gelatin and boiling water until the gelatin is dissolved.
• Keep the mixture in a bowl set over warm water so it does not set while you work.

Create the blue stripes

• Cut the set blue Jello into 1-inch strips.
• Remove every other strip, leaving alternating blue stripes and empty spaces.

Fill the gaps with red

• Pour 3 tablespoons of the red mixture into each empty space between the blue strips.
• Refrigerate until set.

Prepare the white mixture

• Combine the cold water with two envelopes of unflavored gelatin and let it sit for 2 minutes.
• Add the boiling water and stir until the gelatin is completely dissolved.
• Add the sweetened condensed milk and stir until smooth.

Add the white layer over the red

• Pour 3 tablespoons of the white mixture over the red sections.
• Refrigerate until set.

Build alternating red and white layers

• Pour the red mixture over the entire surface of the Jello and let it set.
• Pour the white mixture over the red layer and let it set.
• Continue alternating red and white layers until all of the mixtures have been used.

Chill and cut

• Refrigerate the pan for several hours or overnight until fully set.
• Cut into long strips, then cut at each blue section to create flag-shaped pieces.