Why is color blindness more frequent in boys?
The reason is the gene is located on the X-chromosome. Since men only posses one X-chromosome they are more likely to be affected as they only need to have 1 defective gene. Considering women have 2 X-chromosomes they would need to have the defective gene on BOTH chromosomes to suffer from colour blindness.
As for the above responses: Women have 2 X-chromosomes there is no garuntee which one she pass to her son, so the only way a women will know for sure if she is passing on colour blindness to her son/daughter is if she herself is colour blind (ie 2 defective genes)