If a star moving towards the earth, then the star will appear to be ___in colour.

If a star is moving towards the Earth, its light will be blue-shifted. This means that the star's light will appear shifted towards shorter wavelengths, including the blue end of the visible spectrum. This effect is a consequence of the Doppler effect, which is the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave.