Some field coils of the blue G had black color and some had red color. They are both the same.
A very common problem on the old Luxes is the brushes sticking in the tube. Remove the brushes and their tubes from the machine. Clean the tubes with rubbing alcohol and q-tips. Use a small file to file away a slight amount of carbon brush on all four sides of the brush. They should slide beautifully in the tube, easy in and out, once they are replaced. Sticking carbons are very common and make an ozone smell and spark when running.
Obtain a carbon brush SEATING STONE. eBay, vac shops, etc have them. Hold the stone against the rotating commutator and it will seat the brushes, clean the commutator, and stop the excessive sparking. You won't need more than a piece of a stone to complete this. I've had one stone for years.
