Do two people looking at the same color see the same color? I know if I look at red with each eye, one eye has a slightly different shade than the other eye. I wonder what color red would be if I was able to look through someone else's eye.
Color blindness is a result of a defect in the cone receptors in the retinas of the eyes. Color blindness is a male dominant trait, but is carried by the female. One male in twenty suffers from some form of color blindness, but only one in several hundred females are color blind.
Color blindness is the general term used by most people but maybe in this politically correct world we should refer to it as chromatically challenged. However in reality the symptoms range from an inability to see one color, or shades of one color, to a lack of ability to see any color at all. Because it is a result of a cone defect, colorblind people are also prone to night blindness, and may have extreme difficulty in seeing in low light, or their color perception may be greatly reduced in low light.
What color blind people actually see is hard to explain or describe to one who isn't colorblind, and probably equally hard to determine by someone else. To get an idea of the degree of difficulty, try closing your eyes and describing the color green to someone who cannot see or who is totally color blind.
Describe it without using descriptors such as it is the color of grass, etc. With the exception of blue (which has become synonymous with cold) and red (which has become synonymous with hot) it is very difficult if not impossible to describe a color except in terms of things which are that color, or in terms of another color.
Regardless of the level of color blindness involved, almost all those afflicted can see dark objects on a light background. They may see them as shades of gray but they can distinguish. As the level of intensity approaches equilibrium the ability to distinguish diminishes.
By equilibrium I mean that the intensity of the colors involved approach each other (the dark objects become lighter and the background becomes darker).
The most common color perception problems are with certain color combinations such as yellow on green, green on red, red on green, blue on red, red on blue, and red on black. This last is particularly annoying and dangerous, because it means that unless we are concentrating, those flashing little LED displays become almost invisible. I have almost no perception of LED displays unless I am up close, and the diode is very bright.
By contrast since color blind people don't see color the same way others do, we tend to come up with combinations that are offensive to others but may be neutral or even pleasing or to us.
Some color blind people tend to gravitate to bright, vivid colors because they can be detected more easily. Muted colors or low intensity colors (text, lines or bands where there isn't enough color to register) cause difficulty or are indistinguishable.