Colorblinding is described as 'Chrome extension that simulates the website as a color vision impaired person would see' and is an app in the OS & Utilities category. There are more than 10 alternatives to Colorblinding for a variety of platforms, including Mac, Online / Web-based, Windows, Google Chrome and Linux. The best alternative is Sim Daltonism, which is both free and Open Source. Other great apps like Colorblinding are Vision (Freemium), Coblis (Free), Colorblind Web Page Filter (Free) and Colour Blindness Simulator (Free).
If you are not suffering from a color vision deficiency it is very hard to imagine how it looks like to be colorblind. The Color BLIndness Simulator can close this gap for you. Just play around with the sample picture or upload your own images.