Question: I'm just learning photography and I found this picture 

<http://www.michaelkormos.com/blog/a-lovely-afternoon-family-photography-nyc-family-photographer>

The background was warm with yellow soft tones ... but the subjects are clear. I wondered how can I do that?

Yesterday I did a test, but failed ... lOLz ... It was a bright sunny day at the lake nearby and I changed the white balance color to warm and shot with the flash on her face. But ... her face become darker, as seen in this picture:

![Lake BSB and forest](https://farm6.staticflickr.com/5784/22887832505_b52defc5f7_z.jpg)

I want to know how to make her skin tone natural. Which flash gel should I use for this?

Another case, I did this shoot at night with very low light. 
I used off-camera flash and shot at the subject but I saw my flash became blueish, like the garden lamp. Here is the picture:

![2015-10-19_07-11-23](https://farm1.staticflickr.com/595/22262648996_70ce8d7c07_z.jpg)

how can I fix this color and, if possible, could you reference an article or book that can help me learn more about color and white balance?

Answer: 
You can get different white balance on subject and background when you use flash and gels. That's one of the points of using flashes.

<http://neilvn.com/tangents/gelling-your-flash-for-effect-blue-background/> 

<http://neilvn.com/tangents/photo-shoot-progression-of-an-idea/> (and many more on his blog)

The white balance of the flash is fixed. The color of the ambient light/background is fixed (assuming it's not affected by the flash). If you want a background warmer than the subject, put an opposite (cold = blueish) gel on the flash and then do white balance on the subject. The background will result warmer than the subject.

Of course you have to tune the intensity of the gel depending on the actual difference in color: if you want a background much warmer than the subject, but it is already sunset and you are lighting the subject with a flash, you may not need a gel at all: the flash is daylight and the background is already warm.
It's basically about how you use the gels and white balance in combination. Your subject is lit by the flash. Your ambient background is not. So you can make a color temperature difference between the two, in any balance you want, by adjusting the color of the light on your subject, and then white balancing to match.

If you want a warmer background with a neutral subject, then gel your flash to be cooler (blue), and then shoot or post-process to warm up the entire image until your subject is neutral. The background, which was its normal temperature in the original shot, is now even warmer. On the flip side, if you want your background to be cooler (say, turning a grey sky blue), then gel your flash to be warmer (orange/yellow), and then white balance the image in-camera or in post to get a neutral subject, but a cooler background.

See: <http://www.slrlounge.com/simple-way-change-color-sky-camera/> for good visual examples.