Vision is described as 'is software allowing people with different kinds of color blindness (colour vision deficiency) to see more colors'. There are more than 10 alternatives to Vision for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Google Chrome. The best alternative is Sim Daltonism, which is both free and Open Source. Other great apps like Vision are Color Oracle (Free, Open Source), Colorblinding (Free, Open Source), Coblis (Free) and Colorblind Web Page Filter (Free).
Color Oracle is a colorblindness simulator for Window, Mac and Linux. It takes the guesswork out of designing for color blindness by showing you in real time what people with common color vision impairments will see.
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.
Transform your iPhone into a real-time color blindness vision device. 30 FPS video! This app simulates the most severe deficiencies. It's all in real-time. Just launch the app and look at the world around you through your iPhone.