I think the killer is Minty Fresh.
Minty Fresh and Fancy Guy (our victim) were the only ones that went to the pool before day 2. So, here's what i think that happend.
When Minty Fresh and Fancy guy were sitting in the pool, Minty Fresh first drowned Fancy Guy, which killed him right there, but if he left it like that, the murder whould've been too obvious, so Minty Fresh went to the kitchen to get a knife (Since i and Colourless were watching TV in the living room and no one was walking around in the first floor, nobody would witness him going to the kitchen), and quickly went back to the pool to cut half of his arm of and half of his body, causing Fancy Guy to bleed out, which is also why the water is red. He then took the half of his body and the half of the arm he cut of and left the crime scene (which is why Fancy Guy's legs weren't at the crime scene), along with the knife, washed the blood of of the knife, placed it back in the kitchen, and got rid of the body and arm parts he had.
I change my first action.
Day 14: Push Brown into the fire, and pull Blue away before Brown can pull him into the fire. I'm not letting Blue die that easily.
Day 17: Hide from mint with Blue in the forest
Day 18: Build some shields and drink and eat with Blue
Day 19: Use bow and arrows with Blue to kill Mint, and protect with our shields we bould in case Mint tries to attack us