If a star were travelling at 99% of the speed of light, directly at Earth would we see it? Stars being flung from black holes in the news made me question if something were heading directly for us at the speed of light, would we even know?

Update: Since it's impossible for a star to travel at the speed of light, would we see it coming if it were traveling at 99% the speed of light? and if so, how much warning would we have?
Processes energetic enough to accelerate a star to 99% of the speed of light are not known. A close interaction and ejection from a multiple black hole system could perhaps provide enough energy, but such close interaction with black holes would probably rip the star apart before it could reach such excessive speeds. Hypervelocity stars are known. They have speeds less than about 1% of the speed of light.

A star travelling through space at such speeds would also have problems.  It would be slamming into interstellar gas. I have no idea if it could even survive, or would it be eroded by the interaction with the thin gases in interstellar space.

A star at that speed would be significantly blue-shifted. This would make its spectrum very odd.  A small dim star could be visible, catalogued and observed to have a very odd spectrum at a distance of about several hundred light-years. It is likely that we would first observe such a star several hundred years before it got close to us. However such high speed objects probably don't exist.