I love how Colin is surprised and taken aback when Marina says Penelope cares for him...

He's like: "Penelope?!??!?!! No way that she cares for me.... it's not like I send her more letters than anyone and she actually replies to them unlike my own family and it's not like she always smiles when she sees me and it's not like she tried to warn me not to marry a woman I barely knew and that she's the only one who seems to be interested in what I have to say about things. But Penelope???? No way she even thinks about me when I'm not there 😝😊🤪"

I feel like he doesn't understand that Penelope likes him until the very end of S2 and even then, he doesn't completely understand how deep her feelings are and that's then why he also doesn't understand that he has feelings for her, too. He's just stuck there thinking that's what normal friendships are like... he's so sweet and so so innocent