Red green does not mean that you ONLY have problem with those 2 colors. Means you will have problems with ANY color which is composed of some of the 2. Also the

Red green does not mean that you ONLY have problem with those 2 colors. Means you will have problems with ANY color which is composed of some of the 2. Also there are Red/Blue Green/Blue... basically any combination. So relying in only colors is just bad design.