There are different levels and types of colorblindness. Deuteranopia, Deuteranomly, Protanopia, Protanamoly, Tritinopia, and Tritanomaly
Each one has different characteristics.
The milder varients are the "anomaly" classes. These are the most common forms (specifically Deuteranomoly) and people with these variants can actually go through life without having any major issues about it. These two are caused by having one type of cone on the retina that still works, but not as well as they should. Most people who have these types of colorblindness have very little effect in their daily lives because one color type will "shift" towards it's opposite, but they can still see some degree of that color. They can name colors correctly at a high rate of accuracy. This is actually due to the person learning that certain colors that they see are associated with the names that people label them. They might not see the same color as everyone else, but they are not really impeded by this fact.
The three more serious forms are caused by the complete absence of a certain cone type. For these people (like me) it is more obvious even at a very young age. They are effectively totally blind to one color on the spectrum. They will still be able to name colors correctly more often than not, for the same reasons, but they will have a higher rate of inaccuracy because they are effectively blind to one color. These forms which are called dichromacy, are rarer than the trichromatic anomalies described in the preceding paragraph are.
So in essence, just failing a colorblindness test does not mean that you are really "colorblind". In actuality, it is much more likely that you are slightly impaired. I'm considered to be truly colorblind because all greens appear brown to me (even though I correctly label things green about 50% of the time, but I have a theory as to why that happens.)
Eitehr way, I leave you all with this: (I can't read it :mrgreen