How is colorblindness diagnosed?

His diagnosed as soon as the guardian of the child observes that the child cannot distinguish any colors and is simple. Other types of colorblindness vary on how hard it is to tell wether or not they have the disorder however they are all officially diagnosed the same. A Ishihara color test is used to determine exactly what type of colorblindness they have and to what degree.

http://www.webmd.com/eye-health/tc/color-blindness-topic-overview