The article is misleading. The first boarding group also includes Chairman's Lounge and full fare customers.
The second group (blue) is the first half of the booked load to check in. If there was 120 pax it would be seq. 1-60. If there was only 40 pax it would be seq 1-20.
You could arrive at the airport an hour and a half before the flight. If half of the booked load is already checked in you will be given a silver boarding pass.
The system works extremely well. I am yet to see a punch up with this new system.