Device-dependent colors relate to the settings of the device on which the image was created or output. Device-dependent colors require all devices in the workflow to be “calibrated” to obtain consistent color reproduction. In other words, the input devices (for example scanners or digital cameras), monitors and output devices (for example digital color printers) have to be tuned to each other to make the colors match.
Differences may even occur between devices of the same type or model, because they may have different settings. Monitors may have different brightness or contrast, for example.
For more information on device-dependent color, see the Adobe Acrobat Help.