A tool for verifying a user interface (UI) design of a mobile application receives a screenshot of the application's UI operating at a target device and retrieves a reference UI design image that corresponds to the received screenshot. The tool generates a plurality of images based on discrepancies between the screenshot and the reference UI design image. The plurality of images include a set of differential images in which each pixel location has a value that is based on a difference between corresponding pixels at the same pixel location of the reference UI design image and of the screenshot. The plurality of imagers also include at least one blended image that is an overlay of the reference UI design image with the screenshot.