I had a quite busy day today so as a quick post here is a tool that can help you show white color in the entire screen with just a click.
The application is called White and come very handy if you wish to use your computer monitor as a light box or just want to check the dead pixels on the screen. This tool will surely save your time in setting the display settings to the white color.
Just download the tool and double click the exe file to have your computer screen filled with white color. Press Escape button to exit from the mode, though the application will keep running in the background unless exit from the Taskbar.