It's rare for a sequel to be better, but Color Rush made it work.

STORY - What sets Color Rush as different from other BL series is the unique premise it set: the world where there are monos and probes. The exposition has already been done in the first season but the continuity was done rather imperfectly leaving more room for improvements and questions. I think the pacing per episodes were abrupt and could've been better where there were proper buildups to certain segments and not just an out there happening. Some of the questionable portions that could've been better includes (but not limited to) the following:
1. The introduction to Sehyun and Yeonwoo's dynamic. I may have missed it in Season 1 (if there were any) but there were really no explanation on how close SH and YW were.
2. Hinting that SH was normal or a regular person or so YW thought. One of the most memorable scenes is when YW realized that SH is also a mono but it would've been more powerful as a scene if there were hints that YW explicably thought SH is just a regular person.
3. What I really didn't like the most is how the reveal that Yeonwoo's mom is dead was done. Aside from the mono-probe storyline, YW and his aunt are primarily looking for the missing mother/sister but for it to be done out of frame is really unfulfilling. We didn't even see how YW reacted, how the funeral went, or what the implications of the discovery were.

ACTING/CAST - Yoojun is phenomenal, as always. I really see a bright future in him and I can envision him being one of the biggest male leads in the future should he venture into the more mainstream acting. His delivery of lines, expression, and emotions are really impeccable. He totally reminds me of a younger/smaller Yoon Kyunsang with his looks.
By the way, what made me watch Color Rush S1 is actually the OST since I'm a very big fan of Lovelyz and honestly, I wouldn't have watched Color Rush S2 (or wouldn't have been THIS eager to watch it i.e. watching the 8 episodes all at once right after release) if there weren't major changes, not even Yoojun's acting could've made me. I'm not saying it's Hyunjun's fault but I just don't find myself any more interested, but when Hyuk got casted, I knew I'll be tuning on to this. Some may only know him as a VIXX member but Hyuk is an award-winning actor. His acting debut wasn't on a web-series nor TV, his acting debut was on a film in 2016 where he's part of the main cast. He won the Shanghai Film Festival's best new male actor award for his debut movie! Since then he's done TV series and movies aside from VIXX/solo music and as of now, he hasn't done a single movie where he isn't the male lead/cast. Why am I saying this? It's because I saw that a huge portion of the Color Rush 2 viewers is against him and his character. Hyuk's acting was great, his expressions are superb and his line delivery is equally as amazing.
For the two male leads, they have really done a great job in depicting various expressions with their faces that warrant no dialogue to deliver a message. Like when YW found out that SH is also a mono or when SH saw that the desktop wallpaper of his sister's a picture of them together.

OST - I'm not very keen on the OST this time but it did it's job. It wasn't distracting (expect from the fact that I spent 2-4 listens deciphering what the lyrics were, it turned out to be "adore" and not "alter"). It wouldn't be appropriate to reflect it with the ratings for OST but I guess the musical timing of Color Rush 2 could've been better.

REWATCH VALUE - I mean, I already rewatched it so it definitely has that rewatch value. But of course the main plot of this season is YW looking for his mom and Yoohan being helped by SH so the rewatch value is clearly diminished after knowing that his mom is dead and Yoohan is somewhere filled with bandages on his head.

OVERALL - I have high hopes for the third season, and I hope this season will receive as much love (hopefully more) as the first season so it'd have more $$$ to produce a better sequel. Sorry Yoohan, but I guess I'll be rooting more for Sehyun and Yeonwoo ending up together. Why? Firstly, SH and YW has extraordinary chemistry. YW is the mature one but is the one being protected by SH who is clearly more bubbly and childish. Whenever their scenes happen, I couldn't help but admire how their visuals and acting skills complement each other.
Secondly, Yeonwoo is obviously interested in Sehyun as well. He may be looking for Yoohan but it doesn't always have to be for romantic reasons. Yoohan is his probe and he feels responsible for his disappearance. Though of course at first, Yeonwoo doesn't show interest to Sehyun but it's undeniable that he's going to the Sehyun direction. I'd never forget the part where they're about to sleep when Yeonwoo said "Sehyun, look at me." Why will he do that if he isn't falling for SH? He feels safe when he's with SH, he thinks SH is handsome, and he doesn't want to see SH hurt. Yeonwoo may be struggling but surely he's being interested in Sehyun.
Third, this is a boys' love series and I truly love the premise but the soulmates trope can now be abandoned. Why should the monos only be for the probes? Why should fate decide who you're destined with? Should Yeonwoo only be with Yoohan because he's a probe? If these questions are what they'll elaborate on the next season, it'd be magnificent. During SH's daydream by the end, the only thing YW reasoned for them not to be together was because they're both monos... would it be a foreshadowing of what can be a cause of conflict next season?

Color Rush is a perfect allegory to same sex relationships. Saying a mono is only for a probe is applying the same logic that a man is only for a woman, and that's why I'm rooting for Yeonwoo and Sehyun. Hoping for a Season 3 with Yeonwoo, Sehyun, and Yoohan navigating through a love triangle and exposing more about the world of monos and probes.