In a saucepan, combine the dark chocolate, milk chocolate, and heavy cream. Heat over low heat, stirring constantly until melted and smooth.

Remove from heat and stir in the vanilla extract.

Divide the melted chocolate mixture into three separate bowls.

Add blue food coloring to one bowl, purple to another, and pink to the last. Stir each bowl until the colors are well incorporated.

In the fondue pot, pour the chocolate mixtures in layers to create a swirling effect.

Arrange the dipping items on a platter around the fondue pot.

Use skewers or fondue forks to dip the fruits and marshmallows into the galaxy swirl chocolate.