Yup. That's the cathode filament glow you're looking for. Perfect.
Even better news. That means the starter is almost able to light the tube. So you're close.I could also see anode flashing purple as it tries to start.
You have the one with the dial at the back? That's OK. You can still do this. But you'll need both hands. (One to hold the unit and one to turn the knob.) As Steve Roberts said though, the BD-10 is super-well insulated. You won't get shocked. Just keep your fingers away from the metal tip.My BD-10 doesn't have a button, I feel like I should make some kind of momentary footswitch before I attempt this.
As NobleGas posted, this is actually not so good. It means the tube is trying to light down the gas-returns rather than down the bore. (You can't get any lasing action if you don't have the plasma in the bore.)
Now that Steve has posted detailed pictures of where to use the BD-10 on your head, I'd just give that a try. Be sure to be ready to immediately re-install the cover and blower/fan to restore cooling to the head if it lights though! Once the tube lights it's going to get hot really fast, so you need to get air flowing through those fins as soon as possible.
You'll know if it works almost immediately. Both brewster stems will light up with the purple plasma glow you see in your picture of the cathode end above. If your alignment is good you might even get a beam. But even if you don't have a beam, just seeing the plasma is enough to know that the tube is lit.
Once it lights, turn off the BD-10 and set it aside, drop the lid over the tube, and fire up the blower (or fan) immediately. Then run it for a good 8 hrs or so at ~ 7 amps of tube current. Don't run it wide open or it might wink out, but don't run it at idle either. You want a strong arc blasting down the bore to bury some of the gas in the walls of the tube.
After that, see if it will start back up on it's own without the help from the BD-10...
Adam