Blue tickets are flight tickets exclusive to STA Travel. They are available for students and youths (under 30) for many airlines.
When traveling on a 'Blue Ticket' there may be some flight number restrictions.
You will not be able to travel on a 'codeshare' flight. A codeshare flight is when two or more airlines share the same flight. Only one aircraft will fly the route, however the other airlines can sell tickets under their own flight numbers.
For more information please speak to your booking store.