Chrometric is a stand-alone tool that simulates eight types of color blindness, plus some other visual gotchas - check your site and app!
Chrometric simulates eight types of color blindness, blur ("forgotten glasses"), and reduced contrast (a.k.a my laptop screen on a sunny day).
Chrometric is essentially a simple web browser, and allows you to check webpages (not limited to vaadin apps).
According to Wikipedia, about 8% of males are color blind in some way or another. With Chrometric you can easily see how color blindness affects your creations - websites, images, graphs, and more.
This is a phenomenon you should at least be aware about, and probably get to know a little better, so that you know when to watch out. Or better yet, routinely check your creations for potential problems.
Chrometric is a work in progress, and I'm hoping you'd like to contribute; try it out, and let me know what works, what doesn't, and what additional features or modifications you'd like to see. I've already added some thoughts to UserVoice to get us started - vote or add your own ideas. You can also tweet @chrometric and/or #chrometric.