Our star appears "white" because the sun is so bright - filtered down, it does appear to have a yellow hue, just as a red giant appears "red."
Blue-white supergiants would appear as an awful arc-light so bright that it would be intolerable to human eyes - but they do have a blue tinge to them (slightly).
A "habitable" zone means being far enough away from this sort of star to avoid being roasted, either by heat (duh!) or radiations that would blacken living matter very quickly.
So, in essence, you'd be so far out there would be little heat to make such a world very desirable. It would just be a rock in space. Blue-white supergiants are not for man - or anything else.
God help you if you were around when it collapses into a type II super-nova. Or it emits a GRB.
