There are many tests available to measure colour vision defects but the most common is the Ishihara Plate test. This can test for red/green colour blindness but not blue colour blindness. This is the test most likely to be used for routine colour vision screening in schools or medicals.
It consists some Plates so-called pseudoisochromatic plates, each of them showing either a number or some lines. According to what you can see and what not, the test gives feedback on the degree of your red-green color vision deficiency.
A Lantern test is one such test which is used to identify people not suitable to work as train drivers or in marine and aviation jobs or other occupations where the work requires the ability to accurately reading the colours of lights for safety reasons.