well the context was amidst a joke/bit, they were on the same team for both days but had to face off during rock paper scissors, so seungkwan was saying basically, "yesterday you were my colleague (teammate), today you're my colleague," as in, "we're on the same team but meeting like this... " (as rivals/opponents) so i don't know if it was angry or flustered but more like "game on"

so the line hansol said, "i've never once thought of you as my colleague," said was in context of that, but he said it so naturally and romantically that we're all swooning over it because he tends to say these things that sound so romantic and heartfelt without even realizing how hard they hit (a la "i look at you more than you think")