I will be frank and try not to give spoilers as best as I can but: This is not a story you should expect a happy ending from. This is not lighthearted and it's not romantic. Be prepared for lots of dark twists are turns. If you can't handle or are triggered by stories with sexual harassment, stalking or r*pe then you 100% should NOT be reading this.
That being said, if you're into that sort of plot this is a great read. This story made me so physically uncomfortable and left me feeling gross- but I just couldn't stop reading, lol. If you're not familiar with Harada-sensei's works, the thing you have to remember is that they rarely have a happy plot line. They've become quite known for having sick plots to their manga (although they have some great cute/fluffy works), but Color Recipe hit different for some reason. If I didn't know the baseline for the plot before going in, I would've had quite a few shocks from the twists in it.
I think the reason this manga felt so harsh to me personally is because the 2 main characters felt so real to me. They didn't seem exaggerated. The fact that people as sick as the antagonist of this story really exist creep me out to no end. Harada's characters are always so interesting. When I first started reading I was wondering why the art looked so familiar, and then the plot picked up and I went, "Ahh, this must be Harada and I didn't realize." There's just this sick sense of realism with it that made my heart race with anxiety. This is definitely not for the light of heart. It was nothing I couldn't handle but this story was very psychological. I think Harada-sensei does a very good job of showing what trauma looks like in victims and I thought that was a really nice touch.
The only reason I'm rating this an 8 instead of a 9 or a 10 is because it was so disturbing to me, lol. I enjoyed it in terms of story, but I couldn't /really/ enjoy it until a couple days later when I could let it digest. In the moment, this definitely felt like a thriller manga, at least. Actually I think a thriller or a psychological horror would fit this more than "yaoi" would since yaoi is usually associated with romance. There was no romance in this. It's a very messed up story, but it's so well written. I really do recommend this manga but ONLY if you like dark storylines. I don't think I'll reread it because it makes my stomach churn, lol, but it's a very interesting story.