"So you can't see colors at all?" No, that's not how it works. I have protanopia, which is one type of red-green color blindness. I see colors fine. I just can't tell certain reds and greens apart. They collapse into the same muddy brownish tone.
The easiest way to explain it is with test plates. These are based on the Ishihara color blindness test, the one you probably took in elementary school with the little books of colored dots. Hit the toggle to switch between what you see and what I see.
Most people see the number 12 here.
8
5
3
If you can see the numbers, your eyes work the way most people's do. When I look at these same plates, I just see circles of dots. The numbers aren't hiding. My eyes literally don't have the hardware to distinguish the red dots from the green ones.
What's actually going on
Your eyes have three types of color receptors called cones: red, green, and blue. With protanopia, my red cones don't work normally. So while you see a clear difference between a red dot and a green dot, I see them as roughly the same color.
About 8% of men have some form of color vision deficiency. Women almost never have it because the genes for red and green cones are on the X chromosome, and having two copies gives you a backup.
What it's like day to day
Mostly not a big deal. I learned the position of traffic lights instead of the colors. I ask people what color things are sometimes. I've definitely worn some questionable outfit combinations without realizing it.
The annoying part is when information is encoded purely in color: charts where red means bad and green means good, LED status lights, certain maps. If there's no other signal like a shape, label, or position, I might miss it entirely.
How these plates work
These aren't real Ishihara plates (those are proprietary). I built these using D3's force-layout phyllotaxis, which packs dots in a sunflower-seed spiral pattern using the golden angle. The dots forming each number are colored with reds and oranges, while the background dots are greens and yellow-greens.
The "What I See" toggle applies a protanopia simulation filter (Brettel, Vienot & Mollon, 1997) that transforms every color through the same matrix my eyes use. The reds and greens collapse into indistinguishable tones, and the numbers vanish.
That's what color blind looks like. Not a world without color. Just a world where some colors are the same color.