your g6 should have a manual WB....my g3 does. get a photographers grey card(white on the other side). set your g6 to take a manual WB setting,,,,aim the camera at the grey card so that the card covers the whole lcd screen,,,set the wb and save it,,,,it will be save as "custom1" i think.
under manual, it doesn't matter what the lighting is. manual WB will balance the color properly. if you use a polarizer, you set the WB with the polarizer on your lens.
canon also has its zoom browser software that will also correct for WB, but you don't need it
when you WB manually, you are telling the camera that whatever you are pointing at is color balanced and the camera will adjust to it. therefore, if you wanted to WB and you pointed at someing red, telling the camera that this red thing is color balanced, the camera will think the red is balanced,,,,and what you get is everything in your photos tinted to green
the manul for the canon will tell you what shooting modes will accomodate your manual WB.
white backgrounds becomes an exposure issue. i suggest against it for the simple reason that as the cylindrical shape of the glossy cue curves away, it will reflect all that white background and the edges of your cue will appear to fade. you want as little reflection as possible when getting a good photo of something shiny and cylindrical,,....which means certainly nothing light behind you or the cue