I'll zoom out a bit from Bill's excellent answer.Quote:
I will give you an example of the WB problem. the two comditons where the WB lets me down very often is when I shoot in light from a fire or in broad daylight. In fire the colours are not accurate the Warm nature of light is missed and in Broadday light the pictures are more towards the Blue spectrum of light.
the basic point is that if you want good results, you have to take control. The camera has no idea what you are shooting, and it has no idea that you don't want it to offset the temperature of the light at that time. So, you have to take control and make the white balance what you want. one way, as Bill showed, is to set the temperature yourself, rather than setting the camera to auto. Another is postprocessing. If you want the finest control of white balance, you will get more by shooting raw and adjusting in postprocessing, because in that case, NOTHING about white balance is baked into the file. But either way, the key is not a more expensive body. It's taking control of the process.