I don't think the "reality-check" tag is appropriate here because of course there's nothing realistic about moving faster than light anyway.
So the answer must ignore all the relativistic stuff that happens as they approach the speed of light, and just regard light as an energy transfer with a limited speed (like sound)
First of all, they could not see anything behind them, because they're outrunning its light. So what happens if they look backwards? Complete darkness.
Secondly, there would be severe doppler-effect type issues for seeing anything in front of them, so depending on how fast they're going, visible light might well be increased to a frequency that is outside the visible spectrum, and infra-red is now in the visible spectrum.
But the key here is that all this is happening through evolution. Evolution is a gradual process, so as they evolve the ability to move at higher speeds, they must also evolve the vision sense to see light frequencies higher than we can, as well as process information at the higher speeds - otherwise the high speed ability would be useless, cause them to kill themselves by crashing into things and therefore they would be removed from the gene pool, and the faster than light evolution would have never taken hold.
That being the case, they are most likely evolving the ability to see each other while moving at FTL speed, even though the light itself would form nothing like their shape as we think of it, their brains would have evolved to reprocess the information into the correct shape so what they would "see" would a correct image. (Similar to how our brains process the two separate images from our two eyes into a single 3-D image)
Of course they will only ever be able to see within a limited field of vision in front of them. The light from outside that field simply isn't reaching them.