He likely has selective mutism which is related to anxiety. The character who told him not to speak, was likely meaning it as in "don't force yourself" in order to not stress him out or upset him. He obviously feels calm and comfortable enough to speak around the M.C in certain situations, or he feels he simply has to speak and it's more of a flight or fight reaction.
Hearing colors, seeng sounds and similar things. I honestly don't think the notebook he is carring has anything to do with it.
He's not "hearing colours or seeing sounds" ffs, he has selective mutism related to trauma. Which is why he can communicate verbally at times where he feels comfortable etc. In later raw chapters we see that when Pink hair was younger, he was involved in a car accident where his mum's injured/dead body was on top of him.
At first, I thought the chairman has unlawfully locked him in there. Chairman kinda seemed creepy how keeps an eye on Li Qing through his office so I thought maybe out of jealousy he beats Li Qing when he converses with other people but I don't think that's the case, also for it having the psychological tag this manhua isn't dark at all, idk know anymore Σ(っ°Д °;)っ
Can someone enlighten me why in the earlier chapter Li Wing always ask Xiang not to speak? Why he always ran and startled when Xiang speaks. I thought he couldn't hear. And then later Li qing and Xiang talk normally like the earlier incidents didn't happen. Because I really wanna know why Li qing is acting like that towards Xiang in the earlier chapters.