Using a blender, crush 1 cup Skittles® until there are no whole pieces. The smaller the better, really.
Whip heavy cream using a mixer (hand or stand) until stiff peaks form.
In a separate large bowl, whisk sweetened condensed milk, butter, and cake mix. If you choose to color your ice cream, add a little food coloring in now.
Fold the cream that you whipped into the cake batter mixture using a rubber spatula until completely combined.
Gently fold in crushed Skittles®.
Pour into a 2-quart container and cover. Freeze at least 6 hours.
Sprinkle a few whole Skittles® on top when serving!
Notes
I suggest making this in the evening and freezing it overnight.
Recipe by The Shirley Journey at https://theshirleyjourney.com/skittles-cake-batter-ice-cream/