The colour of a star indicates its

(b) is incorrect because the size of a star does not affect its color. For example, a red giant star can be much larger than a blue supergiant star.

(c) is incorrect because the size of a star does not affect its color. For example, a red giant star can be much larger than a blue supergiant star.

(d) is incorrect because the distance of a star does not affect its color. For example, a blue star that is far away will still appear blue.