EIZO has created a monitor that can simulate various types of vision deficiencies (PDF document). It is great to see hardware vendors making an effort to provide tools to improve accessibility, but this one makes me wonder. Do you really need to have hardware support for this? The advantage seems to be that you can test moving images more easily.
EIZO worked closely with the Color Universal Design Organization (CUDO) (also see english machine translation) in conducting experiments with colorblind test subjects to improve the ability to identify difficult to distinguish colors.
Fore those not fortunate to have access to an EIZO monitor, there are a number of software tools available to simulate how web pages and images look with various types of vision deficiencies:
- Vischeck (which you have probably used if you tried the Web Accessibility Toolbar for Internet Explorer.
- Colorblind Web Page Filter – simulates a whole range of deficiencies such as deutanopia, tritanopia, protanomaly, tritanomaly and more.
What I haven’t seen is an application that isn’t confined to the browser, but works on top of your operating system. I guess this wouldn’t be very hard to do. Depending on the operating system it should be possible to have a filter applied to the entire screen. If you know of one, please post it in the comments below.
This post is not about web accessibility, but I hope you will find it interesting nonetheless. The Stockholm 
Almost a year ago there was a discussion about accessible error messages in the WebAIM forums. Based on that discussion I take a look at how you can create accessible (and usable) error messages for your web applications.