My husband and I went to an exhibition about the solar system at our local natural history museum. There was also an exhibition for children about the human body with really good explanations how genes work, how our ear works, stuff like that.
We came to the part about the eyes and there was an explanation of colorblindness and the different forms together with the tests. You know - the circles with dots where you have to read the number. Anyway, I forgot why but he started reading out the numbers. And well, he got one of them wrong. Not the test for full-on red-green blindness, but he can’t tell certain shades apart.
In hindsight I had noticed that he sometimes confuses names for colors apart from the basic ones or that he doesn’t like it when I identify an object by its color (e.g. “give me the pink one”). But I’d always chalked it up to German not being his mother language.
A lot of people think colorblindness is an on-off switch, if you’re colorblind you only see in black/white/gray or that you can’t tell the difference between red and green but you can see the other colors. But that’s just not how it works.
Colorblindness comes in varying degrees of deficiency and a lot of people fall into that category where it doesn’t affect them in any noticeable way. In fact, for most cases, it may be more accurate to call it color vision deficiency rather than colorblindness. Like they can easily tell the difference between a red traffic light versus a green one, or a red apple versus a green apple. Plus, there are many types of color blindness beyond the well-known red-green type.
So, for someone who can clearly see the difference between a red light and a green light, if they didn’t know any better, they’d assume they aren’t color blind. So unless they happen to connect the dots (pun) after seeing an Ishihara test or just noticing lots of little situations where they’d identified something as the wrong color, it’s very possible to not know. Lots of people have good vision through their young adult life, so never get tested. And most of the time when people are discussing colors, they aren’t getting super specific so you might not notice there’s a difference between Buff Slate Gray and Milky Seawater.
To add experience to your description: I can easily tell the difference between a red light and a green light. I however did not know that the walking person symbol (USA) is in fact white, not green.
I always just assumed it was green until I had an embarrassing conversation with someone from Indonesia I was hosting who said,
“Crossing in this country is so easy; I just wait for the white man and then I go.”
I thought he was just being low-key racist and started to point out that the area we were in didn’t have very many white people around until he clarified he was just talking about the crossing signal.
I can tell the difference between the red and green light - but if a left turn turn light comes on while the red remains (that is only left turns no going straight) I’ll probably miss it because the green is so faint and red obvious