Tim's method works fine. And, as with most things Photoshop, you can get a similar result with an entirely different workflow.
1. Duplicate the layer
2. Switch mode to LAB (Image>Mode>Lab Color) - When given the option do not flatten the image.
3. Open Curves dialoge box (Image>Adjustments>Curves). Ignore Lightness (luminence). In both a and b channels move both the curve endpoint in about a quarter. Don't worry when the colors go weird during the process. They even out.
4. Adjust the opacity of the top layer to suit. I used 68%. Higher opacity = more color intensity.
5. Switch mode back to RGB Color.
This works any time you want to intensify colors. I made an action with all but step 4, which needs to be adjusted individually. One click, instant pop.
michael mckee
My Port Townsend – A City in Photographs – 365