It's probably best to start again with the "mono" version. Even in the JPEG you uploaded there's enough color information to work with, and it should be better in your original, especially if you acquired it in RAW mode.
Try the procedure detailed here by Filipe Alves. Filipe talks about the possible need to color balance before enhancing the saturation, but I didn't find it absolutely necessary with your image. I followed his steps for increasing the saturation, using five steps with the Hue/Saturation tool in Photoshop CS2. The first four saturation changes where about +50, and the fifth was about +25. Be sure to make a copy of the background layer before starting the saturation adjustments, and do the adjustments on the bottom layer with the top layer hidden. Then I used the method from his article he calls the "Easy Way" to smooth out the luminance noise created by the saturation increase, by blurring the bottom, saturation enhanced layer, and setting the blending mode of the top layer to Luminosity.
Here's the result, your image processed with Filipe Alves' method, total time spent in Photoshop about 5 minutes. It's still a little over-saturated in the green and red channels, I think, so tweaking it carefully with the Levels tool by dragging the middle slider to the right on those channels before starting the saturation adjustments should help. I don't think you need to adjust the blue channel, as you can see it's coming out pretty well.
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