a) If a star's spectrum is blue shifted, it will not necessarily appear blue.
A blueshift is any increase in frequency of a light wave. The name comes from the fact that blue light has a higher frequency than red light, so the frequency is shifting toward the blue end of the spectrum.
If a star is moving towards us, the number of light waves reaching our eyes in a second (i.e., the frequency) will increase (a blueshift).
If the star emits red light, the blueshift will make it look less red, but it won’t necessarily make the star look blue.
b) If Star A is closer than Star A and both are approaching at the same speed, one will not appear bluer than the other. The distance from an observer does not affect the blueshift, so both will have the same blueshift.