I have been shooting (small) live concerts with poor env. lightning for some years now with the help of F/1.4 & 2.8 lenses, mostly using a 160th shutter speed to make sure that the fast movements of the musicians are not giving me blurred shots. I also stop the camera down by one stop. I left aperture and ISO automatic and got (IMHO) nice results. 

Here are the original, and the corrected white balance.

![As shot white balance](https://i.stack.imgur.com/P2Ze5.jpg)
![enter image description here](https://i.stack.imgur.com/lc00M.jpg)

The issue is however that the lightning in the locations had too strong color accents, mostly red. I did white-balance correction (using Lightroom) on the photo afterwards but I want to still have less red in the shot since the white balance turns yellow too much into green. So I though I use a flash to be able to neutralize the color somewhat. I am very inexperienced with flash photography and want to find the right way to achieve the following:

* Neutralize some of the ambient colors, but not all
* keep the shallow depth of field of the 1.4-2.8 apertures
* keep the sharpness of a relatively fast shutter speed (100-160th)

I have now seen [this video](https://www.youtube.com/watch?v=HafSg93qnmU) and thought I can use the advice in reverse to preserve color instead of getting rid of it: By using a slow (lower than sync) shutter speed, I could make part of the red go away, but now I am afraid it will blur the picture too much.

So is there any best practice to add some flash into an image to alter the colors more towards white light? How do I control this while still keeping the image sharp? I know I cannot shoot with even an 80th of a second...

I am using a Canon 5D MKIII, Speedlite 600EX-RT and 50/35mm 1.4 lens, shot in RAW.