Dalton is described as 'Find the names of colors on pages with this Chrome extension for colorblindness' and is an app in the OS & Utilities category. There are more than 10 alternatives to Dalton 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 Dalton are Vision (Freemium), Colorblinding (Free, Open Source), Colour Blindness Simulator (Free) and Colorblind Web Page Filter (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.