A color vision test can be done in numerous ways. We like to use the Ishihara test, in which the test embeds numbers or shapes in a plate of multicolored dots. A color-blind person will be unable to identify the shapes or numbers. People who are not colorblind will see the numbers or shapes clearly within the group of dots.
If you have a properly functioning color monitor and you cannot read the numbers within the four circles below, it might be possible that you belong to those individuals that have a certain form of color blindness.