Colorblinding is a Chrome extension which shows how a website will be seen by people with various types of color blindness.

There's support for Red-Blind / Protanopia, Green-Blind / Deuteranopia, Blue-Blind / Tritanopia, Red-Weak / Protanomaly, Green-Weak / Deuteranomaly, Blue-Weak / Tritanomaly
 Monochromacy / Achromatopsia and Blue Cone Monochromacy.

To try this out, just click the Colorblinding button in the address bar and choose a condition from the menu.

Whatever you select, Colorblinding applies an SVG filter to alter the appearance of your page and all of its elements, including images and videos.

The menu remains open, too, so you can click each option in the list to quickly see if there are any problems.