I'm lousy at distinguishing black from deep blue, even in good light. Is this a thing?

See query. Not looking for medical advice, just interested. A long time ago I spent time in UI/graphic principles, and am aware, in general, of the bioscience of, say, why you don’t put certain lettering colors on others as a matter of perception, so that’s where I’m coming from.

And, although this is probably obvious, when I’m not wearing glasses and stuff is fuzzy, it’s even worse.

And for years I thought my own couches were leather dyed black, and lo and behold, Mrs. Bloom tells me they’re deep brown, which I can agree to only if I try real hard.

Is this a “colorblindness” thing like green/blue equivalence?

Black and navy blue can be hard to distinguish from each other. When I worked in the apparel business the trick the old timers used was to hold or get near the fabric of questionable color (FOQC), close your eyes and mentally ‘picture’ either black or navy for a couple of seconds. Then open your eyes and you can tell if the fabric is black or navy. I know it sounds silly, but I have used it myself several times when sorting fabric in a warehouse.

I have some form of Tritanomaly, meaning fewer blue receptors than typical. I can’t tell Navy Blue from Black except in very bright sunlight. Blue-green mixes just look green to me. I suspected this a for a long time, the first confirmation was when I saw an online test card about 10 years ago, and finally last year I saw an ophthalmologist who tested me with a complete set of cards to finally verify it.

However, as far as I can tell, a lot of people have a problem distinguishing between black and Navy blue.

Until you figured this out, did you think the Smurfs were some kind of horrible racist joke?

As a kid, I loved baseball cards, and for a long time, I thought that the New York Yankees’ uniforms were white with black trim.

They’re not?

/Not a joke.

/OP here. Told’ja.

I wear black and navy dress socks. Got in the habit of buying different patterns of each - the only way I could avoid wearing black/grey slacks w/ navy socks.

Landed color-blindness.com, all I could ever want at my level of interest/concern.

But maybe I have something I can add to my CV!

There are past threads on the subject. The red, green, and blue receptors pick up ranges of colors, the ranges overlap, the range varies among people, they don’t all have the same percentages of the different color receptors or total number of them either. Color-blindness is defined differently for different purposes. In my case the main problem has been the number of conversations that include “What blue one? I only see green ones.”

I used to think I was blind or weak in blue.
Used to work in a cut n sew shop working with marine textiles and we had a navy blue fabric that you could tell was blue only in direct sunlight. It looked utterly black under artificial light. This coupled with the fact that all the women in my immediate family, by both marriage and by birth, seem like they are all tetrachromats. They all see some variety of blue where all us men-folk in the family see grey. All my kids were born with, according to them, blue eyes. I would have said, and almost got in an argument with my first wife by insisting they were grey (they *were *grey! dammit!)
But, according to every test I’ve ever taken, many professionally administered, I’ve tested normal for color vision.

How does this webpage appear to you? Does the straight dope banner at the top look black? How about people’s names (I mean this: Mijin)?