There are many tests available to measure colour vision defects but the most common is the Ishihara Plate test. It was named after its designer, Dr. Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917. It 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.
This test is the most widely used for testing for red-green colour vision deficiency and contains 38 plates of circles created by irregular coloured dots in two or more colours.
The plates will be put in front of you and you will be asked what number you can see on the plate. Some plates contain information which people with normal colour vision can see whilst others contain information that only people with colour blindness can see.
If you make a certain amount of errors you will be diagnosed with colour blindness. Special Plate tests have been devised to diagnose young children who are not old enough to identify numbers.
Try a search on the internet for it where you can undertake it free of charge.
1. Farnsworth-Munsell 100 HueColor Vision Test
2. Color Arrangement Test
3. RGB Anomaloscope — Color Blindness Test