Looking for a yaoi manga

I don’t know where I read this but I wanted to see if anyone could help me out. It was about two guys gate keeping a gate (don’t know what the gate was for, I think people pass it like a afterlife kinda thing) both love each other but can’t touch each other. I think they are representing in colours, like good and evil maybe?? . If they touch their afraid of contaminating each other. It’s a short story and they give in to their love and have sex with each other, only to swap colours or roles, so it’s a happy ending.