Poor or uneven lighting can wreak havoc even on perfect skin. If your skin doesn't look natural, a small touch-up or two with Adobe Photoshop can quickly correct it.
Using the Right Tools
Open the image in Photoshop and examine what needs correcting. In our example, the skin is a bit too blue. We could probably correct this just by changing the Color Balance, which is available by clicking Image, Adjustments and then Color Balance. However, this doesn't give us much control over where the adjustment is applied.
Because we want to adjust only the skin tone and nothing else, we'll first select the skin using the Quick Selection Tool. Pressing Ctrl-C and Ctrl-V copies and pastes the selection into a new layer.
Choosing an Adjustment Layer
Click the Layer menu and select New Adjustment Layer. From here, select the appropriate adjustment. Since we're adding some yellow to the blue tones, we'll choose Color Balance. If the skin was only a bit dark or a bit light, we would use the Brightness/Contrast option instead. Depending on the photo's issues, Selective Color or Hue/Saturation could also work. When you select an adjustment layer, a new layer is created in the Layers Panel with adjustment options presented in a new Properties panel.
To reduce blue highlights in the skin, drag the Yellow/Blue slider towards Yellow. Click the Tone menu and change it to Midtones and then Shadows to adjust those tones as well.
If the skin tones don't look quite right in some places, do some touch-ups with the Brush Tool. Click the Foreground Color swatch in the Toolbox and specify the skin color. Remember, you can use the Eyedropper to sample a color from the photo. Select the Brush tool in the Toolbox and adjust its size as needed in the Options bar. Click the Mode menu in the options bar and select Overlay.
Create a duplicate of the Background layer by dragging the Background layer in the Layers Panel onto the New Layer icon. Paint over the areas you want corrected. Fade the overlay into the background by reducing its Opacity in the Layers Panel -- an opacity of 20 percent usually makes the touch-up brush strokes unnoticeable.
Another way to clean up blemishes or inconsistencies in the skin tone is to use the Clone Stamp Tool or the Healing Brush Tool. With either of these tools, Alt-click a place where the skin looks great and then drag the tool over the blemish. Always use a small brush and short strokes when working on a face to keep your work from looking overly Photoshopped.