For years I've used both Canon and Nikon cameras. Often we've shot photos of the same event and at times I've really admired the slightly warmer, richer color of the Canon shots. This is especially true on slightly overcast days or otherwise cool color temperature days.
The Nikon seems more accurate. But who said that totally accurate was always the most pleasing? Sometimes. But not always.
But what makes the difference? It's not color temperature. You can slide the color temp in Camera Raw or iPhoto left and right all you want and you'll never get a Nikon digital SLR to mimic the Canon.
It's not saturation either. You can increase saturation or vibrance in Photoshop but it will only occasionally look a little more Canon like. Not it.
It's not Color Balance.
It turn out though, by using Photoshop's Selective Color correction layer you can mimic a Canon digital SLR very closely. But only by moving the Black slider. Choose the Selective Color. Red is the default color. Perfect. That's where the difference between Nikon and Canon lie. You'll see several sliders:
With the Red selective color chosen in the drop down menu move ONLY the Black slider slightly to the right, from a low of about 15% to a high of around 45% in most cases. It depends on the scene. Use your eye. I usually don't even look at the values as I'm sliding it. I just slide to where it looks richer and more pleasing and then check the value. Sometimes I back off a bit, just to make sure I'm not over correcting a photo.
The effect is amazing! Reds become richer. Not more saturated as when using the saturation layer, but deeper--exactly like the Canon renders them. It has wonderful subtle effects on skins tones when the skin looks a bit too cool and color temp isn't the answer. For example, when the flash just seems to have left warmth in the dust and we don't want to turn our subjects orangish with a warm color temp.
How did I come across this? While perusing www.dpreview.com and comparing their studio still life shot, I noticed that once again the reds seemed to be more rich on the Canon camera versus Nikon. Often it was more pleasing regardless of whether accurate or not. But what was the difference? I noticed that the Reds actually looked a little DARKER, not "brighter" as we get when we boost saturation. Nor does it look like adding red in the color balance. A very different effect!
That led me to try the above. Again, the amount varies by the scene. Some don't benefit at all. That is, sometimes Nikon gets it better, or you just don't want a little extra richness in the red tones.
Summary: This technique is very subtle, not at all like boosting saturation, or doing a Color Balance and adding Red. It also is nothing like adding magenta to the selective color Red channel (or subtracting cyan). Try it! That Black slider on the Red selective color is the key.