Sarah Lane's app cap from iPad Today 208 was Dulux Visualizer CY from a well known UK paint brand, Dulux. This app lets you see what any of your rooms would look like if the walls were painted a different color. It uses augmented reality through the iPhone or iPad's camera so you can actually see a live view as you switch between colors. Just tap on a wall or surface that you'd like to visualize, and the app will detect the edges of the wall. You can also change the color of multiple walls at once.
Dulux Visualizer suggests color schemes to go with the furniture in the room. Then, because Dulux is a major paint brand, it will show you where you can buy that paint color. While it's clearly geared toward this brand of paint, it still is very useful whether or not you choose to buy from Dulux. Dulux Visualizer CY is free, and is a universal app that runs on iPhone and iPad. There's also a version for Android in the Google Play store.
To see a demonstration of Dulux Visualizer CY, check out iPad Today 208 with Sarah Lane and Leo Laporte.