Photoshop has two adjustments that both control the strength, or saturation of colour – here’s a comparison
The Hue/Saturation adjustment is likely to be the most used one of these two adjustments, however not always the best option.
Use Photoshop’s Vibrance adjustment to improve colour when there is a person in your composition, as this will save skin tones from becoming over-saturated.
Here’s a look at the two adjustments on the same image…
As you can see in this comparison, the Vibrance adjustment has a very subtle effect on colour. Boosting the Saturation slider as well helps to pump up colours around the portrait, but in general the colours are very similar to the original.
The Saturation adjustment applies a much harsher effect on to colours, but notice that the skin turns very orange compared to the original above.