If you're running auto white balance, don't. Actually set it to daylight or flash, or to a kelvin setting in the 5000-5500K range. It almost looks like you're running auto white balance and it's balancing the blue out to grey.
Depending on what power setting your B10 is set to, the strobe color temperature will vary quite a bit. At full power it will be 5500-5600K. As you dial the power down, the strobe electronics will cut the duration of time that it is powering the flash tube, which results in the light shifting to a bluer spectrum as the power is dialed down because most of the red spectrum a strobe emits is during the last part of a full power discharge. You also see this behavior with speed lights. The other behavior you'll see with larger power units and older technology units is the color temperature will get warmer as the power is dialed down. This is because as you dial the power down, the electronics lower the voltage that is pumped into the flash tube, which results in the light getting warmer. Very few strobes do the necessary voltage AND power duration changes (usually it's one or the other) needed to maintain a consistent color temperature over the full output power spectrum. The ones that do, very prominently advertise that they do because it's a big deal in strobe land to have the same color temperature over the full range of power that you can set the strobe to. Most strobes either get warmer as you dial down the power or get cooler as you dial down the power depending on if they change the voltage or change the amount of time powering the tube. Smaller power units like speed lights and the B10 usually get cooler, higher power units usually get warmer.
In terms of getting correct color balance, ideally, you'd want to shoot raw, and once you determine your power level for the strobe, use a whibal card (not a grey exposure card, an actual white balance card) and take a picture of it, then proceed to shoot the rest of your photos. Once you've pulled the raw files into your converter of choice, use the white balance picker to set the white balance of that first image, then duplicate the white balance settings to the rest of the images taken at that same power level.
Other than that, if you're shooting JPEG, set your camera white balance to either daylight or flash. It'll render a little blue, but your background should come out looking a lot more correct.