There are many different methods of doing this, but i have found this the most effective.
1. Carefully select around the part you wish to colour change.
2. Copy and paste the selection to create a new layer. (or press Ctrl + J)

Desaturate the layer (Ctrl + Shift + U)
3. Go to Image > Adjustments > Color Balance.

Turn all settings up to 100 on the color that you want, on midtones, shadows and highlights.
4. Set blending mode in the layers box to Hue.

you could use color, but hue has a better finish.
Here is the final result.
Any questions? i will try my best to answer them.
-Nicecar-