I'm creating a universe where ftl space travel is possible by folding space. You can only travel point to point with direct line of sight.
The example I plan to give in the book, to clarify, is that day you are a circle on a sheet of paper and you want to get to a square on the other side. Instead of travelling through the entire sheet of paper you fold the paper over in the third dimension and travel vertically next to the square. The paper then returns to its previous state and the objects in the teleported location swap places.
I was wondering if it would be reasonable to do a blue shiftish thing since an object is approaching so quickly. I'd like the sky's colour to drastically change in an observable way, but over a bit of time so that the protagonist thinks it's weird. Does this sound too far fetched or is there a scientific way to explain this?