Who is granted the right-of-way when changing lanes?

There are basically two answers to your question:  1)  The traffic enforcement laws that have specific language that details what driver responsiblities are in any given traffic enforement area.  For example, a driver with a green light can proceed through an intersection.  2) Civil laws or tort laws use a "reasonable person" standard in any given situation despite the traffic enforcement laws.  For example, if a driver has a green light and notices that another car is proceeding into the intersection and blowing through the red light, the driver with the green light would be acting "reasonably" if they stopped despite the green light.   If the driver with the green light did not stop despite the awareness of the other vehicle and an accident occurred, the difference between (1) and (2) would be:  If a driver has the right of way and does not act "reasonably" they will not be cited  and probably will not get a ticket (1) above.   However, the same driver who does not act "reasonably" could be partially at fault for the accident and resulting damages which means the driver with the green light might have to involve there insurance company (2) above.

KPS