Enhance --> Adjust Color --> Replace Color --> Use the color picker to select the color you want to change, then adjust the Hue, Saturation and Lightness to taste. Also pay attention to the 'fuzziness' bar which will widen or narrow the range of affected.
Play around with this feature to see all the different options.
There are loads of PS tutorials online that will walk you through the features step-by-step.
I use PS Elements so if you're using full PhotoShop, the path to make the changes may be different.
HTH