I find most of the colors too hard on the eyes.

Number 4 I think is the most of appealing. The less saturated teal is easier on my eyes.

Something else I just noticed concerning the image of the side-by-side spines. I take it the straight spine is the health one. People tend to look at things from left to right; therefore, someone may interpret this as, "the poor guy went in healthy and come out crippled". : )