First take a photo of your truck on a semi cloudy day to avoid extreme highlights. Bring that into Photoshop. In Photoshop create Paths around everything, it is a bit tedious, but if you get everything separated, it will make the next step easier. Use the Hue/Saturation (Under Image > Adjustments) with the "colorize" box checked and you can get some great colors and it keeps the highlights and shadows basically intact. You can use the other tools to lighten, darken, contrast, etc.
Though I find it much easier and fun to look at photo galleries of your truck online and go to car shows.
Good luck.
