Here is a short tutorial about how to use the information found in color channels - in this case, how to use LAB color mode channels in an RGB document. Here is our photo, in RGB space with the Channels palate activated.
First, start by converting a copy of your photo to LAB color mode. Image>Mode>Lab
Then, highlight the A or B channel (usually you'll get more information from A, but don't write off B altogether!)
As you can see, we can't see a whole lot yet, but wait ... watch what happens when we invert (ctrl+i)
The value relationships now make more sense, but it's too faint to make out much detail yet, so let's adjust the levels. Adjust your black point so it's just at the start of the histogram curve, and adjust the white point so it's just at the end of the curve.
Now this is the information we want to put in our document. So just select all (ctrl+A) then copy (ctrl+C), and go to your original document and paste it in. Now the adjusted A channel is it's own layer in our RGB document. To get the color back, I've set it's layer blending mode to Luminosity as Phischer mentioned in the other thread.
And that's about it. Start healing and cloning your heart out from here!