In the video, a person is holding a smartphone and using an app to change the color of the icons on the screen. The app is called "iColorizeLabel" and the person is using it to change the color of the dock icons. The person's finger is seen moving across the screen, selecting different colors for each icon. The app allows the user to customize the color of the icons, making it easier to identify and access different applications on the device. The video demonstrates how the app works and how it can be used to personalize the user's smartphone experience.