The fun with ice continues! In ongoing experiments freezing things in ice, I decided to try freezing food coloring in the middle of an ice cube. Then when the ice melts, the coloring will release and change the drink.
The first step was to make perfectly clear ice. Then I heated the stubby end of a bar spoon in a pot of boiling water and kept plunging it into the ice until I made a tunnel.
And finally, all was black.
The ice I use to fill the hole after adding the food coloring is very cloudy, but I don't think it's so terrible.
This method could be used to add other things to drink beyond color: perhaps it could be filled with bitters, or citrus oil, or absinthe to change the flavor of a drink mid-way through it.