The blue budgie is interested in interacting with the Quaker who wants nothing to do with him. The Quaker is being low key defensive, but I think if the budgie had pushed it, the Quaker would have been more aggressive toward the smaller bird. You really have to keep tabs on those budgies as they are afraid of nothing until they get injured; only then do they gain some respect for the larger bird.
Two of my budgies picked an altercation with my CAG and were lightly injured before backing off and learning the CAG is not interested in interacting. I even have a semi-opaque curtain I close around the CAG's cage when the smaller birds are out so they do not land on the cage bars and get injured. But I found the injured birds trapped in the undercage waste drawer are crawling under the curtain to get closer to the CAG! Luckily no bone were broken, only one wing strained and the other had a bleeding bite. Both budgies recovered completely, but no longer try to get closer to the CAG.
That being said, I have one cock budgie, Sky, who has decided he is going to be friends with one of my cock cockatiels, Pogi. Sky courts Pogi as if he were a hen and has even tried to mate with him. Cockatiels are so laid back, most of them, all Pogi does is open his beak in threat and cage locations in the birdroom, but never attacks Sky. I have never had my cockatiels injure another bird. I have had lovebirds injure 'tiels, and my Senegal will punish an aggessive small bird by pinning them to the floor or a cage top and ripping feathers out of their back... Sunshine Senegal's aggression toward the small birds has all but disappeared now that she lives cage free and the only aggression I see now is when she reminds the budgies to BACK OFF!