Colors on your shirt will fade by washing. It’s easy to make it vivid again on the photo by increasing its saturation level using a photo editing program. This trick work on most clothes and similar materials. Most photo retouching software has the tools to let you select certain area and adjust its saturation level.
Saturation level controls the colorfulness of the color relative to its own brightness. Increasing the saturation level will make it more vivid, whereas lowering it will make it become a gray-scale image.
For GIMP Users
You can use Rectangle Select Tool (R key), Ellipse Select Tool (E key), Free Select Tool (F key), Fuzzy Select Tool (U key), and Select by Color Tool (Shift+O) to select the area you want. Free Select Tool works best for most cases.
When doing selection, try to hold Shift, Ctrl, Shift+Ctrl to do selection adding, subtraction, intersection.
To adjust the saturation level, click “Main Menu” > “Colors” > “Hue-Saturation…”. Increasing the Saturation value will make the selected area (the cloth) looks newer.