![Ishihara test image seen by those with differing colour vision.](http://static.sciencelearn.org.nz/images/images/000/002/313/full/Colour-vision-problems20161104-16395-11i6j3q.jpg?1674167970)
Colour blindness is the decreased ability to perceive differences between some colours. It usually has a genetic basis and affects men more than women.
Colour blindness is the decreased ability to perceive differences between some colours. It usually has a genetic basis and affects men more than women.