I am currently at chapter 60 or so, and I am wondering about the use of color in this comic: as far as I can tell, red represents Mian's psychosis, as it only ever pops up whenever Mian slips into her deranged avenger mode and starts alternating between injuring Haegu and demanding sex from her. Blue, meanwhile, represents blood and gore, but also some aspect of Haegu's character that I cannot quite put into words yet. Anyone has any ideas about that? I've also noticed that sometimes when Mian and Haegu get it on, the red and the blue mix into purple for a bit.
About the colors, it's as you said, red is for Mian whenever she sees things, like haegu or her dad playing with her mind, it also shows up when Mian gets deranged, or demanding, her eyes even turns red when she's in that state of mind. Meanwhile Haegu represents blue, her eyes will turn blue too in the upcoming chapters when she's in a deranged state of mind.
As for blue and purple for bloody, gore and bruises scenes, I think it's just to make the scenes look less disturbing, I think the scenes would look way too disturbing if they showed up blood and bruises in red.