In one of Greg Igan books, IIRC - Dichronauts, different wavelength of light have slightly different speed.
The stars with high proper motion look like colored lines - blue at one end and red at another.
If star is faint enough then you cannot see the color with naked eye but you can see the dash-like shape anyway. Though in order for the dash to be long enough to be seen with naked eye you need to have slow speed of light or relatively high star speed.
(though in Dichronauts there will be A LOT of other tell tale signs that you are in another world :) )