"….when we returned after failing to fix the first task, I was…. in Gryffindor…. nothing was better between us then either…."
-- Albus Potter (CC3.11)
Harry Potter visits his son Albus in his room inside the Slytherin dormitory at Hogwarts. They talk to each other about what has happened. Albus tries to explain why he wanted to save Cedric Diggory. Harry listens and apologises for suspecting Scorpius Malfoy of being evil, but he and Albus are still uneasy with each other (CC3.11).
After the previous event - likely early October 2020
This event takes place in the Repaired timeline, as described in the essay "Albus Potter and the lesson in Quantum Mechanics" by Nick Moline.
Albus notes that "Green is a soothing colour isn't it? I mean Gryffindor rooms are all well and good, but the trouble with red is – it is said to send you a little mad…." (CC3.11). During Harry Potter and Draco Malfoy's time at Hogwarts we only every see everything about Slytherin House from a negative point of view and, of course, green light is associated with the Killing Curse.
From the Web
Pottermore: Harry Potter and the Cursed Child
The theatre production opened in the West End of London at the Palace Theatre on 30 July 2016, with Jamie Parker in the role of Harry Potter and Sam Clemmett as Albus Potter: Harry Potter and the Cursed Child, Parts One and Two