Color-coding isn't just for stoplights and poisonous frogs; many movie scenes are adjusted to bring certain colors out of the screen to manipulate how the audience feels. Remember the scene where Laura pulls Riggan aside and tells him about the little person that might be growing inside her? The reds in that scene really stand out. It raises the intensity and licentiousness of their tryst, which is weird because it's not really a covert relationship.
And compare this redness to the blues and greens that tend to permeate the rest of the hallways and stage of the theater. When the fake fog rolls out for Laura's monologue, the set has a very mystical blue glow to it, just like the darker blues we see in on the wings of the stage. But when we shift backstage to Mike and Leslie, getting in bed for their sex scene (during which Mike actually tries to have sex with her), we get more of red again.
Then there's the stark yellow of the room during Riggan's confrontation of Sam about smoking weed and the following monologue. The bright yellow lighting mirrors the increase of intensity and almost seems personal to Sam as it stands out from the rest of the color palette. Hey, Mike does tell her she stands out from everyone else.
And speaking of Sam's monologue, there are actually quite a few of these long, scathing speeches that characters give one another, and there's something special about the way they're filmed.
Notice when Sam is yelling at her father, we see the whole thing from Riggan's perspective. We are looking at Sam as if Sam were talking to us. This does a few things. First, it's kinda scary and intimate, as if Sam is a real person talking to us. There are no cuts to break things up, no pans back to Riggan and back to Sam— it's just us and Sam in one long, uncomfortable take that we can't escape from.
Secondly, it doesn't allow us to see Riggan's reaction. We know he's standing right behind the camera, on the receiving end of all of Sam's spiteful words, but we don't actually get to look at his face and see it change and react like you might expect from a normal movie. But leaving it up to the audience to interpret his reaction is in some ways more powerful. It's not hard to imagine what Riggan is feeling because we're feeling it to, and when Sam has finally wrapped up everything she has to say, we see the immediate sense of regret spread across her face and can interpret exactly what she's looking at.
Finally, we might imagine these monologues at the camera as mimicking actors in a play. In a play, monologues and asides allow the audience into the thoughts and feelings of the characters (e.g. Riggan's monologue to the audience about the old couple in the car accident).
And Sam's monologue isn't the only example of this: when Riggan confronts Tabitha, the camera stays focused on Riggan although we can perfectly imagine the affected, calm, smugness on Tabitha's face. And we get the same effect when Riggan talks to Sylvia about his plane ride with Clooney and Farrah Fawcett. This shot is almost painful because Riggan's obsession with himself and his own relevance has never been more apparent and we can only imagine what Sylvia looks like as she has to endure the knowledge that Riggan hasn't changed.