Red, but if a person has a disturbed perception of red - protanomaly, then he will see blood dark green, gray, maybe brown.
There is such an application for Mac / iOS michelf.ca color blindness simulator. In it you can simulate how color blind people with different color blindness options will see the picture. Aside from curiosity, it is very useful for visually impaired interface design.
I will answer with a line from the song - xs, an experiment is needed
But seriously - it is very difficult with color blind people, well, especially if it is congenital - explain to a blind person what color is.
I, along with my color blindness, often come across people who begin to point me to different objects and ask what color I see them. But the fact is that it is impossible to show a person with normal vision what colors we see the world in, because color blind people do not just see green instead of red, this question is much more complicated.
Imagine that you are shown two almost identical colors and say one is dark green and the other brown. You simply cannot determine which one is red, but you know roughly how they look.
Color blind people do not merge yellow with blue, they merge different shades of certain colors. For example, with one of the color perception disorders, shades of dark green, dark red and light brown colors may merge. There is a line between them, we can see which of these colors looks darker, but it is difficult to accurately rank it as one of the three options. Very.
There are violations in which dark yellow and light green merge, but that's another story. There is also indistinguishability of shades of blue (and I have this) - blue, purple, lilac, etc. are simply divided into dark and light shades.
Answering your question - what color does blood look like to us? Yes, in general, exactly the same as for you. It's just that there is a certain shade for the red color, which in combination with certain shades of some other colors looks very similar, and sometimes indistinguishable.
For example, you will not have any questions about identifying the color in the picture below:
The most difficult thing comes when the color is not just clean and light on the screen, but, for example, on a jacket, which is a little dirty, a lamp gleams on it, and the lighting is also incomprehensible. For a person with normal vision, this is perceived on an intuitive level,but for my reduced color perception it is literally a disaster :)
My grandfather was a surgeon, while he suffered from color blindness. He confused red with green. Grandmother said that he saw her exactly dark green. Unfortunately, I couldn't ask my grandfather personally, he died when I was a little girl.
I can answer as a person with certain difficulties in terms of color perception: oddly enough, we see blood red, although a dark red color can sometimes seem to be something like brown. The overwhelming majority of color blind people do not have problems with identifying primary colors, troubles appear when determining shades (pink, brown, gray, etc.)
In general, it seems to me that color blindness is a rather individual thing, and although the previous speaker rightly pointed out three main types of this deviation, the differences will be stronger with regard to the color perception of individual objects.
Color blindness is a visual disease that manifests itself in the inability to distinguish some colors. There are several types of weakening of color perception:
Protanomaly - difficulty in perceiving red. People with this type of color blindness confuse red with brown, gray, black, and sometimes dark green.
Tritanopia is the absence of blue and purple tints in the perception of the color spectrum. In this case, the person sees blue and purple as red or green.
Deuteranomaly is the difficulty in identifying green. There is a mixture of green with orange and red hues.
From this we can conclude that color blind people see blood brown, gray or black.