Sometimes people are born with colour blindness. People who are colour
blind find it hard to distinguish colours. The most common kind of colour
blindness makes it hard to distinguish red and green. There are more men
than women with this type of colour blindness, because it is caused by a
copying mistake (mutation) in a gene on the X chromosome. Girls have two of
these in every cell, so if one of these carries the mistake, she usually has a ‘backup
copy’ that is correct. But boys only have one X chromosome (plus one Y), so if
they inherit a chromosome with the mistake, they will be colour blind.
But clever scientists are finding ways to help colour blind people
see the colours that they normally can’t. They have created glasses
to help the eye distinguish between the different wavelengths of
colour, allowing people to see the world the way people without
the mutation can.
Dogs do not see red colours; only blue and yellow and their combinations