Here's a recent photoshop project where I needed some references for hair and skin colors: the image on the right is the original, at left is the (heavily) photoshopped version.
The first step is being clear on why you want to change colors. Sometimes just getting white balance correct is all you are looking for. This tutorial is for those times you are trying to create a color that is difficult to get from the original (as in the above example), or create a new color completely.
You might simply be experimenting to find something that looks good. For those times (like the shirt in the sample above) you can simply adjust hue, saturation and lightness until it looks right. Another goal is to try to change something to a target color. I wanted the hair and skin in the photo above to match typical sample colors.
To match to a color, the first step is get color swatch(es) of the color(s) you need. I've assembled a reference image containing hair, skin, sky and water colors you can use at the end of this post (below).
To change existing colors in Photoshop
Again, the simplest method is to select a color range using the Hue/Saturation tool and then adjust the hue slider and mask out any areas you don't want changed. But in areas with complex highlights or shadows (such as hair) this sometimes doesn't work as well as you might prefer.
So either because you want to match a specific color, or for more advanced control, try Jim DiVitale's method instead. First, create three different layers of the same color, and set them to these blending modes and opacities:
- Top layer: color/50% opacity; Middle layer: overlay/25% opacity; Bottom layer: multiply/10% opacity. Feel free to experiment with different opacity settings. For example, if you're lightening dark hair, change multiply to screen.
- Insert a Hue/Saturation layer as the top layer of the group to give you more subtle control over the look of the new color if you wish.
- Group all these layers and add a mask for the entire group.
To change colors, you simply paint on the group mask to reveal or hide color changes! You can also create a second group of a similar color if you want to have slight variations in the color you are applying, or blend both together in a master group mask to average two (or more) colors.