Are you colour-blind like 5% of European male population? This is the question that will receive an answer here. You will even know the exact form of colour-blindness is yours when browsing to test your colour vision.
You will have to check little images like the one here and indicate what you see (not everybody sees the same thing, it’s not as simple as you’d think first).
Then, the test will speak and you’ll know. It’s barely less precise that a pro optician or a physician eye/vision test. It’s based on exactly the same elements.
See also: Color-blindness and spftware specification.