"color blind" is a term of art, there is not actual color blindnessbut there is a fault in the development of either both sets of the retinal cones that percieve the color light and transmit info to the optic nerve. Color blindnessmay be total or partial; total is much less common
2 major types of color blindness : 1. trouble distinguishing red and green meaning they have moderate severecolor vision defectcaused by complete absence of the red retinal receptor and which green retinal receptor are absent and are moderatley affecting the red receptor. is the most common type color vision inhereity.
2. those who have difficulty between blue and yellow is very rare and meaning there is only 2 cone pigmentsand a total absence of the blue retinal recpetor.