Add a little red food coloring to the butter you are melting.
To get true red or black colors, buy paste food coloring from a craft or cake decorating supply store.
When the red butter is melted, pour it over the popcorn as usual. Caution: Red paste color may dye skin
Pop up some corn, air popper, microwave, pan popped.
Melt some butter, whatever kind you prefer, and add some red food color to it.
Pour over popped corn and mix to coat.