Okay either way, if it's really photoshop, best suggestions I can provide are: 1) Play, play, play. There's a lot of stuff involved in that program, lots of features and unlimited things you can do.. pretty much. 2) Search Google - look for things like "photoshop tutorials" or "how to photoshop" if you know the version you can do things like "photoshop 7 tutorials" or "beginning photoshop 7".
Photoshop is a great program, but unfortunately there's no magic button that says "Click to Color Left Fender, Right Fender, Rear Fenders, Gas Tank". It's just not gonna happen that way. Since everything is 'shaded' every pixel has a slightly different color - to make things look real.
It takes a LONG time to get really good at any of the graphics programs out there that are worth anything.
Then again, you can click on the paint brush icon, select your color and go crazy! haha.
The use of Photoshop and "Photoshoping" is an art as well. The truth is (just like some people can draw, but others can draw very well) you either have the talent to suck, be alright, or be great at it. As stated above the grafx' programs take a LONG time to be good at!!!