MISCONCEPTIONS AND COMPENSATIONS

Color blindness is not the swapping of colors in the observer's eyes, just the resolution. It is analogous to myopia: is that fuzzy blob one long bus or two short ones parked end to end? Grass is never red, and stop signs are never green. The color impaired do not learn to call red "green" and vice versa. However, dichromats often confuse red and green items. For example, they may find it difficult to distinguish a Braeburn from a Granny Smith and in some cases, the red and green of a traffic light without other clues (e.g., shape or location). This is demonstrated in this simulation of the two types of apple as viewed by a trichromat or by a dichroma.
Anomalous Trichromats are often able to readily spot camouflage clothing, netting, and paint that has been designed for individuals with color-normal vision. For the same reasons a color-blind painter might use too much blue to paint a green foliage landscape, a similarly color-blind artillery spotter would perceive too little blue dye used in camouflage created to match the same landscape.
Traffic light colors are confusing to some dichromats: there is insufficient apparent difference between the red and amber and sodium street lamps and the green can be confused with a grubby white lamp. This is a risk factor on a high-speed undulating road where angular cues can't be used. British Rail color lamp signals use more easily identifiable colors: the red is really blood red, the amber is quite yellow and the green is a bluish color.

However dichromats tend to learn to see texture and shape. This lets them see through some camouflage patterns.[1] In the apple example, above, they will see the clear difference because the surface pattern is different.

Color blindness almost never means complete monochromatism. In almost all cases, color blind people retain blue-yellow discrimination, and most color blind individuals are anomalous trichromats rather than complete dichromats. In practice this means that they often retain a limited discrimination along the red-green axis of color space although their ability to separate colors in this dimension is severely reduced.

It should also be noted that even though some people are unable to see some or maybe even any of the numbers in (e.g. red-green) color blindness test, the person might still be able to tell the difference between the colors in his or her everyday life.