1) try to select the area you are trying to change the color of. (if you don't know how look at the tutorials in the newbie
playground.
2) go to adjustments -> Black and White
3) add a new layer (you should be familiar with layers, you've worked with photoshop.)
4) change the layer blending to overlay
5) color in the areas you want to change the color to ( i.e.change the shirt to red, paint the new layer area of the shirt red)
6) Deselect (Ctr+D)
...finished.