why is there a bright blue ball on the pigeons front bumper when you use couplers

i see a bright blue ball on the front bumper on the pigeon when i turn on couplers

edit: its actually a bit brighter than tow hooks balls
edit again: i found tow boom controls in d series so i think they are adding tow trucks. also i saw these balls in other cars

 

That is probably a hookup that the developers are planning. Like to hook multiple vehicles together

 

That's how you connect stuff to other stuff

 

It's a tow hook (passive, receiving end).

All official vehicles have it, not just the Pigeon. The definition of the coupler is usually buried somewhere in the body file.

 

This, sometimes it's in the bumper file too, for example the D series.