Teri,
What you are asking involves two sets of skills, and I am not sure which you are trying to learn about.
First, there is altering the color. In the Photoshop Help Section, use the index and look up words like "Color" and "Hue" and study all sub-sections pertaining to "changing". Also, look up "Blending" and "Blend Modes" as that can come into play as well.
Second, there is altering part of the shot, but not all. In the Photoshop Help Section, use the index and look up words like "Selections", "Layers" and "Masks" and study all sub-sections pertaining to "tools" and "using".
Brush up on those two skills and you will have it.
Oh, notice that in both cases, the first step is to open the Photoshop Help Section. This is a little known and under-utilized technique that can assist with a multitude of Photoshop questions.
But now you have two places to start.
Rad