What is it?
The Soft Proofing feature is a useful tool for photographers to preview and predict the color and tonal changes that will occur when an image is printed, output to a specific device or converted to a different profile. A new feature in the Proof Setup menu allows you to preview the effects two common types of color blindness have on your image, giving you the ability to see how a color-blind person will view your image.
Why is it important?
The most obvious use of the Color Blindness proofing is in Web design. To ensure that visitors to your site can read the text against a colored background, previewing your design with the Color Blindness profiles will help identify any problem areas. This is particularly important as more photographers are building their own sites in Photoshop, either to slice up for use in Dreamweaver, or to build the site completely using a tool like Sitegrinder. Ensuring all visitors can access your site is a fundamental component in building an effective Web site.
Bonus Tip: Color blindness is thought as an evolutionary advantage in detecting certain types of patterns. This was useful as hunter gatherers and is useful today in detecting certain types of camouflages. Today, approximately 5-8 percent of males and only 1 percent of females are color blind. More fascinating information on Colorblindness can be found on Wikipedia