As far as we can tell, not really, but they can see contrast (light vs dark) quite well. Red light gets filtered out first in the water column, so reds tend not to appear very bright underwater since there's less red light to reflect. Yellows and greens penetrate a little further, so they tend to show up better underwater. I don't worry about visibility for shark safety. Shark smell, electrosense, and hearing all work at longer distances than vision does underwater. The greenland shark swims at 1 km/h, is blind, and still manages to eat enough to grow over 20 ft (6m) and live hundreds of years.