Which two colors are primarily tested in color vision tests?

The primary colors tested in color vision tests are red and green. This focus is largely due to the common condition of red-green color blindness, which affects a significant portion of the population. Most color vision tests, such as the Ishihara plates, are specifically designed to identify deficiencies in the ability to perceive these colors.

Red and green receptors, or cones, in the retina are essential for distinguishing between different colors. When these cone types do not function properly, it leads to difficulties in perceiving reds and greens accurately, which is why these particular colors are strategically used in testing. The design of the tests aims to reveal these specific deficiencies, thus allowing practitioners to evaluate a patient's color perception accurately.

In contrast, other colors such as blue and yellow do not represent the predominant defects in color vision and are less frequently highlighted in standard testing. Similarly, black and white represent shades rather than colors, and red and blue do not target the most common color vision deficiency.