Color blindness can be an issue if one wishes to hold a first or second class medical certification, or does not wish to be limited by the inability to fly at night with a third class medical certification.
However, depending upon the “degree” or intensity of color blindness, you can obtain a
medical waiver that says you are good to go if you pass certain criteria. One of the tricks can be finding a color vision test you can pass with regularity (it can be different between examiners because there are a number of different test options to use).
This is info about color vision restriction from LeftSeat.com but it doesn’t say what happens if one fails the AME or eye doctor tests.
Here is the FAA’s Decision Criteria for those who have failed their screening color vision tests, which varies according to the class of medical certification: http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/ame/guide/app_process/exam_tech/item52/amd/
Finally, it is also important to mention that people can become color blind over time. If you are borderline color blind now and struggle with passing the color vision test, it might be best to try to obtain a permanent waiver early on. Otherwise, you will be tested every exam for the rest of your life. To not pass the test in later years could have a significant impact on your medical certification.
To your good health,
Advanced Senior AME
Heart Attack and Stroke Prevention
Family and Sports Medicine