Dull photo, bright photo, dark photo, saturated colors etc. In images we usually get these terms. When we capture a photo from camera or scan by scanner and see them in computer, most of the time we are not satisfied by their color, contrast, or brightness.
So we have lots of options for color correction for our images and mover over we have Camera Raw processing in Photoshop, by this you got full control over colors for your raw images.
To learn about basic of colors go to Color basic tutorial.