there are many ways to adjust image color in photoshop
this answer refers photoshop 6.5 or above
open your image with photoshop and try one (or combination of) the following:
from the menus choose
1. image> adjustments> levels
2. image> adjustments> color balnce
3. image> adjustments> hue/saturation
every one of those will open up plate to lets you control and change the colors
and the tons and their depth etc
you'll have to play with them a little and get to know how they work
very soon you will be able by using them get the right colors for you picture
good luck