Well no judging going on, it justhelps to know what we're dealing with first.
I can't help you with the G5 but 5D will be similar to my 350D.
Regarding white balance on the 5D you probably want to do a custom white balance. This involves taking a photo of a piece of white paper so that it fully fills the frame and then telling the camera that that previous photo is white. If you read about custom white balance in the manual it'll give you a better how to than that.
BTW, if thats the Ultrasonic 25-105 then you have a pretty decent lens there. Ok, not L glass standards but personally I was impressed with it when I tried it.