Have you been getting photos like this with your off camera flash? The reason for it is you have a mixed lighting situation. The background is tungsten or 3200º Kelvin and the subject has flash or 5500º Kelvin.
By doing everything pretty much the same, except for two changes: the flash has an orange gel on it to match the tungsten and then the white balance for the scene is set to tungsten.
I prefer to put on the orange gel over the flash and then use my ExpoDisc to get a custom white balance by pointing the lens to the flash with the ExpoDisc in front to help me get an accurate skin tone for the subject.
I prefer not seeing the orange and green backgrounds in my photos when using flash. If you do use the gels as shown, you will fly through the post-production. Many people try and remove the color shift in the background with post-production. However, the time it takes to convert the flash to the correct gel combination, you’ve corrected everything you shoot in the same situation.
Imagine shooting a wedding or an event where you may have hundreds, if not thousands of images to color correct if you don’t use the gels.
The sample above is the regular flash under fluorescent light. There are more color differences from my experience under fluorescent lights than under tungsten. Just because you see a fluorescent light doesn't mean it is going to be green. Some of the lights are already daylight balanced and will give you proper color with a flash.
Here you can see the shift to a better skin tone and background not as green, because I used a green gel over the flash.
While this may take between 2 - 5 minutes to set up properly, if you do it often, you may cut your time to 2 - 3 minutes to set up. It is very important you see this in your over all workflow. 2 - 5 minutes once or 2 - 5 minutes for every photo you shoot to color correct it. It is your choice. Depending on the situation you might not have time. If you had the time and didn't do it, you will be wishing you had during post.