Add the milk, cream sugar, vanilla and vodka to a blender. Run until the sugar is dissolved.
Pour the ice cream base into the bowl of an ice cream maker. Run the machine until the ice cream is the texture of whipped cream.
Divide between five bowls. Tint each bowl a different color: red, yellow, orange, green and blue. Place back in freezer for 30-45 minutes.
Add the colors in "blocks" in the pan. Red on one side, Blue in the middle, Orange on the end. Pour the green and yellow lengthwise across the top and smooth out.
Place in the freezer until solid.