In your photo editing software, open a digital image---whether from a saved file, uploaded directly from a digital camera or scanned from a photograph.
Choose the magnifying glass tool to zoom in on the image so you can clearly see the edges of the hair in the photograph.
Click on the "magic wand" tool (in Photoshop) and use this to select the hair. This tool may also be called a "quick mask" or "auto mask" feature in other programs. If there are lots of highlights and shadows in the hair, the tool may only select a portion of the hair. You can expand the selected section by holding down the "shift" button on the keyboard and clicking in the area of hair that you want added to the selection.
Use the "lasso" tool if no magic wand tool is present or if sections of hair cannot be selected with the magic wand due to a lack of contrast between the hair and the surrounding portions of the photo. This tool may also be called a "mask" tool in some programs. The lasso tool selects a portion of the photograph by allowing you to click along the edge of the area you'd like to select.
Adjust the brightness to make the hair color lighter or darker. In Photoshop, brightness is found in the "Image" menu under "Brightness/Contrast." In other photo editing programs, brightness may also be found under a "Photo" or "Edit" menu.
Adjust the color balance to change the hair color to a different hue. The color balance tool is found in the "Image" menu under "Adjustments" in Photoshop. It may be found under the "Photo" or "Edit" menu in other photo editing programs. You can change the hair color by adjusting the balance between cyan and red, magenta and green, and yellow and blue. For instance, to make the hair color more red, you'd slide the color balance slider away from cyan and toward red. This method will maintain the hair detail and the different tones of the hair.
Save the image once you're happy with the result.
Print out the photograph on photo paper if you're changing your hair color in a glossy photo.