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.

Yeah, especially since ive been officially tested for it multiple times, have other people not?

I'm surprised this didn't develop into another fight. How did he react to you saying he was color blind? Or did he figure it out first?

Data presentation software has safe colors option.

Color blindness affects 8% of Caucasian males, very rare in females.

I guess it's pretty easy for him. It seems like he has a very mild form and can't tell certain shades apart. I think it was something like yellow and grass green or red and orange. So he hasn't had any noticable problems.

I constantly got grades deducted in shop-class for using the wrong resistors (even though my calculation were always right). Even kept arguing with the teacher about how I did't use the wrong one ... but we never put it together.

I only found out a couple of years later during the conscription physical. Then it all made sense ...

Yes

There are several different types of color blindness, so it depends. In case of reds greens blindness I think they see both as grey.

You'll usually see red as red and green as green. It's just that under some lighting conditions they look the same, so your brain will has to pick one. For the most part there are enough context clues for your brain to figure out what colour it actually is, which why it can go unnoticed for a long time, especially if only have a mild version.

I have a type of color blindness called tritanomaly, which is blue/green deficiency. I can still see most greens and some blues but there's a range I can't see. They're sometimes gray or silver and other times I can watch the color kind of vaguely flicker between silver and blue while looking at it. We discovered it when I was a teenager but I didn't officially get diagnosed until in my 30s.

1% of females as well, but few know that even though there must be a lot out there.

Thanks, I didn't know they had a name other than "colorblindness test" :D