Baker CharlotteSometimes uploaded this video of a cake with seemingly magical, color-changing frosting to her YouTube channel back in November, but it’s only just now started getting noticed by the Internet. The clip shows a cake with a wavy frosting pattern, airbrushed with yellow, orange and pink food coloring. When she spins the cake stand around, however, the cake seems to change color and now has purple, blue and green frosting!
Although Charlotte didn’t explain how she achieved this effect, a few helpful commenters explained that the wavy, textured frosting pattern is the key. A special frosting tool creates two-sided ridges in the frosting, and the airbrushed food coloring is then applied carefully at an angle so as to only hit one of those sides. Then, the cake is spun around and the other side of the ridge is airbrushed with a different color.