There are a number of online tests available to identify if a person is color blind. Tests are offered by the Colorblind Home Page, Colblindor, EnChroma and more.
Although tests are available online by the resources listed above and others, it is recommended to have the test overseen by an eyecare professional.
Ishihara plates are widely used as the method to detect color blindness.The pseudo-isochromatic plates created by Dr. Shinobu Ishihara, feature a colored number against different colored backgroundplates, and candetect red and green color blindness, according to Colblindor. Additionally, the Colorblind Home Page offers a free test along with information regarding the spectrum of color blindness, and EnChroma provides resources for correcting the visual impairment.