If you use Photoshop, you'll need to tell it what color space you want to work in. A working space uses a specific range of colors (depending on which one you select) for all the images you create. Photoshop displays accurate colors by converting the colors from a working space to your monitor. If Photoshop knows your working color space (the source) and your monitor (the destination), the program can do its color conversion intelligently. This entails choosing your color settings.

Simply choose Edit, Color Settings. In the Settings pop-up menu, choose Web Graphics Defaults if you're a Web designer. If you primarily focus on preparing graphics for print, choose U.S. Prepress Defaults unless you're going to print your images in Europe or Japan.