True color blindness is very rare. Most "color blind" people are red-green color blind and can still distinguish between e.g. red and blue.
Either way the "incomplete" forms of colour blindness are one of the most common forms of disability, so using color as the only distinguishing factor in consumer cable types is pretty exclusionary.
As long as you use fairly different shades of red and green, they can still match the cable to its matching color shaded port. Much UI accessibility is based on this fact.
Having to go even further than that and use shades of the colors I do have trouble with would be far more onerous.
Additionally in the physical world how are you going to determine the shade of something relative to something that is not present? i.e if you only have one cable in front of you. We don't have absolute perception, it tends to be affected by context, additionally the lighting now seriously affects your judgement... The reason this is so different to colour is because luminescence is a single receptor type (rods), with which you are trying to compare intensity of an area of one type of signal filled with other detailed information; whereas with colour you have three signal types (cones), in combination and at a lower detail than rods, so it's effectively separate information with at least 2^3 completely distinct permutations to differentiate in almost any lighting or context. This also explains why the absence of only a single cone receptor type has a significant impact on perception since it drops to 2^2 halfing the completely distinct permutations, of which two are merely black and white, so you actually drop from 6 to 2 non-monochromatic permutations - so you see it is far more challenging using either shade or partial cone types.
At some point there will always be someone who something doesn't work for. You suggest using symbols, but what about people who are completely blind?
So you use something like a combination of color and braille, and then the rare person who is monochromatic can use the same solution as someone who is completely blind.
So your basically saying screw them all since it's impossible to include everyone? I just outlined for you the most common disability, it's particularly easy to avoid since they can still actually see.
> the rare person who is monochromatic can use the same solution as someone who is completely blind.
...how would you like to be told to learn brail in old age just cos your eyesight isn't quite good enough to read some small print?
No, that's just awful. Shape first, colour purely as an extra, then brail if the symbol is not relief or discernible enough, this is absolute basics of accessibility. This also helps everyone and functions in very low light since we all have low sensitivity to colour compared to luminescence, more so the older you get
Your disposition is needlessly antagonistic.
Moreover, regardless of what is common to every standard cable, anyone is free to put their own labels on their own cables to suit their needs. Not every solution has to be complex bureaucratic uniformity.
> I just outlined for you the most common disability, it's particularly easy to avoid since they can still actually see.
Are you even sure that color blindness is more common than blurred vision that makes it hard to discern small symbols?
If you say so, but it seems necessary to counter your apparent lack of empathy for people without perfect vision. I don't feel bad at all about that.
> Moreover, regardless of what is common to every standard cable, anyone is free to put their own labels on their own cables to suit their needs.
Now you're just bending the discussion to your will.
How is that any more helpful than me accusing you of an apparent lack of empathy for people with vision that can discern colors better than small symbols?
> Now you're just bending the discussion to your will.
Your argument was that not making all cables in a way that addresses all needs is saying "screw them all" to anyone else. But nothing has to work that way because total uniformity is not actually mandatory. It's completely reasonable to have a default that works well for most people and use something different for the people who need something different.