This feature is common in many image-editing packages and may also be found in your scanner driver. What you want to do is locate an area in the image that you know is white. The control will be an eyedropper or something to that effect. Once you click the eyedropper onto the point that should be white, the image will brighten up without losing any detail or color. Here is a comparison of what happens when you have insuficient image resolution.
Color is the biggest headache of digital printing.
Matching the colors you see on your monitor to what the printer produces is virtually impossible without investing in specialized equipment and software. In most cases, however, your customer is looking for colors that come close. Reds are red, blues are blue, and most important, flesh tones appear as they should. The easiest way to achieve sufficient color is to use pre-matched links or profiles that work with your printer. Use this function if it's available.