This may seem obvious to some, but it had never occurred to me before, so I thought I'd share in case it's helpful to others.
Last night I was at a photography course (on lighting, pretty disappointing, actually) and they reviewed white balance issues. They suggested comparing auto white balance with custom in their studio, and when I did, I used my little red purse as my subject. And in doing so, I discovered that although the auto looked pretty close to the light in the room, my red channel was blown. When I changed the white balance and re-shot the picture with exactly the same settings, the red channel was perfect.
I usually think if my red channel is blown, I should reduce exposure... which helps, but sometimes results in a slightly darker image than I want. So the idea that white balance would impact it as well was really helpful for getting the results I really want, both in terms of colour and exposure. Although it certainly makes sense when I think it through, it was just a new revelation to me. So now if I see my red channel is blown, I will probably think to check white balance as well as exposure.