A very simple solution to this problem would be to turn it into grayscale by using the red channel and throwing the other channels away. The red channel doesn't have any problems in this particular picture. This is a quick and easy fix, and then you can colorize the photo if you want.
To do this, open the picture in photoshop and find the channels pallette. If it's not open, then (on the taskbar at the top of the photoshop) go to Window>Show Channels. Look for the red channel and click on it. Then, on the taskbar again, go to Image>Mode>Grayscale. You'll be asked if you want to throw away the other channels, click yes, and you're pretty much done.
You can make it look a little nicer by blurring it a couple pixels. Better yet, duplicate the background layer by grabbing the layer itself and dragging it down to the little page icon at the bottom of the layers pallette and then changing the blend mode to soft light or overlay.
The other methods mentioned are all good, especially the one involving painting in colour mode, but they're advanced.