Sadly, I understand your attraction to this. For me it's the contrast. While the colours are perhaps over saturated, the addition of colour somehow makes this horror come alive and makes it a shocking reality.
Part of the artfulness, is the contrast between what is coloured and what isn't - a conscience choice. The weathered bed and tattered walls provide a strange backdrop and juxtaposition to the body. The femininity of the pale lilac dress and the long hair introduce an eerie beauty to this nightmare. So does the position of her body. It lies almost peaceful...
The examiners concluded it took the killer more than 2 hours to perform this misery. I imagine she died long before he was done.
Edit: I find also something raw about the wooden bed frame and the dirty mattress.