I was asked to shoot a wedding at the weekend, it was ok but I struggled to photograph people in the dim light of the evening reception. I used flash of course but it killed off all the ambient light and the resulting shots had no atmosphere. I tried turning off flash and cranking up the ISO, this worked to keep the ambient lighting but the skin tones were all over the place - red, purple, green from the disco lights.
How do I shoot like pic related? How is it so well exposed and so well balanced?