When I shoot VB, I am usually shooting ambient lighting. My settings the other night were ISO 3200, F2.5, SS around 1/1000. I was using my 135 L lens. When I use my 70-200 2.8 L, I usually endup going ISO 6400, 2.8, and trying to get 1/800 at the slowest. When I shot with my 24-70 2.8, it was ISO6400, 2.8, and 1/1000 ss. Most school gyms are terrible to shoot in. You will need some good glass, 2.8 and better, and shoot ISO 3200 most likely. When I use my 85 1.8, I can go F2.0, ISO 2500, and get 1/800.
When using a speedlite, I never have it on the camera. It is on the rail of the bleacher bouncing off the ceiling, and I have two, one on each side. I am looking into getting some strobes to make it even easier, I hope.
VB in high schools is tough to shoot due to the poor lighting conditions. The yellow is from the lighting in the gym. Gyms are famous for the lights cycling which will cause WB issues. Plus if the bulbs haven't been changed in a while, that will cause it to be even worse as far as WB and brightness.
How high did you push your ISO? You will need to stick with your 24-70 2.8L lens and push the ISO.
This picture was with my 24-70 2.8L lens, ISO 3200, 2.8, 1/500.

Jimmy