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Therefore, a son from a color-blind mother (who receives the trait from his mother on the X-chromosome) will always be color-blind, regardless of the state of the father (who can only give his son a Y-chromosome).
There are multiple causes, but color blindness is primarily inherited by way of a mutated X Chromosome. Due to the fact that men only have one X chromosome, if they are handed a faulty X chromosome (by a carrier mother) they will be color blind. Women on the other hand have two X chromosomes, which is why many less women are color blind than men. The odds that both X chromosomes are faulty is extremely low, and the healthy one will take precedence providing normal perception of color.