I have learned here at RP to always check my channels as the first step in any retouch job. It's a great tip, so I thought I'd pass along the "how to" of replacing a bad color channel... :)
1. Make a duplicate of your image. Select Image > Duplicate from the pull down menu, or right click on the blue bar at the top of your image and select Duplicate. In this image that I am working on, the blue channel looks pretty guilty, so out it goes...
2. Switch your duplicate image to Lab Mode: Image > Mode > Lab Color
3. On your original copy, make the channel you are going to replace active - in this case it's Blue
4. On your duplicate image, make the L (Lightness) channel active
5. On both images, hit Ctrl+A on your keyboard to select the entire image (or choose Select > All from the dropdown menu)
6. Choose the Move Tool, activate the LAB mode image and while holding down your shift key, drag the L channel from the LAB mode image onto the original image behind it on your desktop. Holding down the Shift key will make it snap into position EXACTLY where it should be.
Once your cursor is positioned over the original image, it will turn into an arrow with a box and a + attached to it - let go when you see this and the channel will snap into place.
Replacing the channel makes the color seem funky, but that is usually pretty easily corrected with Curves.