hur hyunjun's acting is good, the way he portrayed go yoo han's easygoing straightforward fun loving kinda impulsive personality.. i didn't think i'd like a boy with mask on throughout the half of a movie this much but his voice did the job. (i actually like him more when he's wearing the mask xD.)
you'll surely learn a lot of color names watching this movie / series. also some random fun facts about colors. the story seems to have ended abruptly & i think there should be a sequel. i didn't read the book it's based on but i'm thinking i should, to know if there's more to their story.., it's a low budget movie with so-so acting and all. like most of the bls out there. but if you're into bls, i do recommend it. it's nice. the group of friends is really fun. also, for me it was intriguing and if you like thinking, or like to read between the lines, this movie / series could turn out to be more than just another romance story for you.

quick comment on the music. they're good on their own (the line "take my hand, i'll let you go" is on repeat in my head xD)
but i don't think the bgm fit in with the drama for many parts. to me, the music seemed out of place at times. the soundtrack is really important for me and i'm not so happy about this one's. will see if a rewatch can change my mind.

one last note, i read some reviews here and there that say this movie gives a wrong / problematic message & encourages unhealthy / obsessive relationship. i don't think that's the case. the protagonist is an unreliable narrator. idk if you're familiar with the notion but yeon woo thinks a lot of his feelings are due to obsession. that's because his mind is preoccupied with fear. he always presumes his feelings are rooted from the possible negative sides of the mono-probe situation. however imo he's not quite correct about this. he was unable to distinguish love from obsession due to the many common / similar aspects of these two feelings.
nevertheless, love and obsession can coexist. in reality, this story didn't really show either of them hurting the other because of that obsession nor did it encourage anything like that. it only exists in the form of fear, rationally so, which they overcome by the end of the story.