RGB Working Spaces and Document Profiles
In an effort to standardize how digital color is displayed and printed, Adobe implemented the concept of device-independent RGB working spaces in Photoshop. When editing your image in one of these RGB work spaces, a color tag or ICC profile is saved with the file that describes how the colors in your image should be interpreted. Photoshop also uses a color profile that describes how your monitor renders color to provide an accurate display of the image. In theory, when viewed on another calibrated monitor in an application that understands ICC tags, the appearance of the image should be the same.
For this to work properly, the digital image file and the devices used to view and print the image need to be characterized with a profile. With this arrangement, the numerical color data can be accurately translated between different profiles by a color-management system (CMS), such as the one that is built into Photoshop. In my experience with Photoshop 6, this system works quite well, and I'm very glad that it's there for me to use. In some workflow situations, however, such as Web design, strict adherence to a color-management regimen may not be appropriate. There are also design environments, such as my own, in which work is being produced simultaneously for both print and screen, and using color management makes a lot of sense.