Different light sources have various color temperatures. For instance, a standard incandescent lamp is much warmer than daylight. Thus, if you have distinct light sources in a scene, it’s impossible to set a correct WB using only White Balance tool.
Luckily, Capture One offers plenty of ways to edit such images.
In some of the cases, you can go with a simple gradient mask. It works well for scenes where you have natural light from a window and artificial light from a lamp.
Things get a bit more complicated if you’re dealing with mixed light sources across the whole image.
In this case, you can create a masked layer from a target color:
Don’t forget to refine the mask – the correction would look much more accurate.
Now, set WB for selected areas to balance color temperatures.