The sons of a colour blind woman are always colourblind but not the daughters because :

the gene for colour-blindness inherited from mother is dominant over the normal gene from father

the colour-blindness gene is a recessive gene borne on the X chromosome and the sons inherit it only from mother but daughters inherit it both from father as well as mother

the female hormone in girls does not allow the expression of the colour-blindness gene in daughters.

the gene for colour-blindness is recessive gene inherited by sons only from mother and the daughters inherit it only from father.