Pipe wrenches are usually red because a red pipe wrench is more visible in a toolbox full of grey pipe fittings. Most plumbing tools are red in color.
Generally speaking, there are three main reasons that pipe wrenches are red, as described next.
Identify brand name
In addition, That color is a characteristic of a particular brand name, one manufacturer (Rigid) does this to identify their product. To make pipe wrenches have used red as a standard color of their plumber’s tools for close to a century. Slowly, it became a custom, a consensus, a culture.

More visible
It makes them easier to see when cleaning up in a dark room, or after laying them down under a cabinet or under a sink where there is little light. White would stand out more. Really, you want to handle a white wrench under a toilet?
Seriously, not all pipe wrenches are red, but it does help to pick up and to find tools at a cramped job site under a sink.
I have ever seen orange pipe wrenches or Stilson (monkey wrench term isn’t used in Australia) red, black or silver are all really common, and blue and green are less common.

Safety signs
In the safety sign, red means forbidden, stop, fire and danger. Prohibited, stopped and hazardous devices equipment, or environment are marked in red.
Red will help you identify potential dangers and daily conditions at the active.
Carrying out daily urgent troubleshooting and preventive maintenance, red pipe wrenches are a product of the occasion.