What's 'white' in the picture isn't so important, as how your camera 'sees' the picture. It's more a case of your camera reading the colour temperature of a scene correctly. Under certain conditions, it won't do this, which is another reason RAW is a handy format to use, as you can just change it afterwards.
If you're talking about setting the white point in the levels function, you don't have
to do that - instead you can adjust the white and black point by hand until you get something that resembles how things looked on the day.
The blue colour cast you mentioned can be a pain. In my case, it's been because the camera has assumed the scene has a higher proportion of red in it than it actually has, or a lower
colour temperature, and has corrected by adding that blue, which has knackered the picture
Cracking article on the theory here:
It takes a big man to admit they are wrong, and I am not a big man.