X-wing markings

They find their own X-Wing easier in the Hangar :-D

 

As Meister Yoda pointed out it could be more for ground purposes, the pilots and maintenance crews being able to tell the ships apart. I imagine it could be useful in flight though, you often saw the X-Wings flying in formation or near each other at the same relative speed where they would have been able to use it to distinguish who was who. Actual aircraft on Earth have various markings too such as tail numbers, liveries for various air forces over the world, warnings and instructions for ground crews, etc. You might not be able to see the tail number on an airplane if it flies by you at high speed but it serves a purpose for ground controllers and would be visible by an aircraft flying nearby at comparable speed/heading.

 

True that's what a callsign is for but that's for radio communications and I was talking more about visually monitoring ground traffic or just the fact it would be visible to another plane flying in formation, same with an X-Wing. Regardless of how fast they're flying if they're flying in the same direction and speed they won't be a blur to each other and those marking would be visible.