I almost guessed:

Personally, it seems to me that the alcohol solution of diamond green, as well as iodine, has antiseptic properties due to alcohol. And they paint them in persistent, unflattering colors only so that it is visible where they are already soaked. The doctors in the fear of their people are blinded."

In fact, most often in surgery, green has been used (and is used) not so much for disinfection (because there are milder antiseptics in the open wound to infuse alcohol), namely to mark the edges of the wound and monitor the dynamics of the healing of the seam.