You’ve had your turn. Now it’s mine.
Let us take a moment to appreciate Bradley James’ facial expressions in this scene.
For the black and white gifs he’s been conversing with his father about how to rule over Camelot. Uther just slandered his son for being a weak king and allowing such a great city to crumble and ruin. The first gif you can tell he’s trying to hold back tears, because he’s realizing he has failed his father and therefore believes he has failed Camelot and everyone in it. Then he begins to realize his father is wrong, that his way can’t be the right way to rule Camelot. But he’s so uncertain, so lost. What he thought was right was disproved by Uther, and some of his words made sense, but he still feels he has failed and doesn’t know what to do anymore.
The last black and white gif is Arthur’s dismay and disappointment in his father, the one man he looked up to and respected his entire life. He’s finally realizing how wrong Uther’s ways were, and can’t believe he wanted to follow in his footsteps.
Now for the color gifs, Arthur’s just been told off by Merlin that he doesn’t need to live up to Uther’s expectations because Arthur always did what he believed to be right, and he’s running about the castle trying to find his ghost father and send him back to the spirit world (of which I believe he’s reluctant to do because it is after all, his father, whom he’s felt he never got the chance to fully build a relationship with and discuss all the things he needed to know to be king. Arthur’s burden of being king is extremely heavy, and he just wants some direction and advice with all this responsibility, and naturally Uther would seem like the solution to his difficult trials).
And now here he is, seeing his father about to kill Merlin, his most loyal servant and friend who has made more sacrifices for him than everyone in Camelot combined. When he’s blowing the horn, you can see the pain in his eyes. The pain that his father would actually try to kill Merlin, which confirms his realizations earlier that his father isn’t everything he thought he was. The pain that he was the one who had to blow the horn, he was the one who had to send his father away, which in his eyes felt like killing his father all over again. The pain that he would never get those answers to his questions, the guidance to his problems, the solutions to becoming the best king he could.
Because his father could never help him in the first place.