You're saying that people should be prevented from getting jobs they're capable of performing because the alternative is to crack open decades old usability texts? There are multiple suggestions in this thread which could be easily implemented at little-to-no extra cost without sacrificing accessibility.

No, its because for certain jobs you need certain qualities. They might upgrade this system, but who knows what else lurks in their basement. Its the same reason why you would not train a severely short-sighted person to be a sniper.

There’s a big difference there: for a sniper, vision is a core skill.

For someone sending alerts, color vision is not — things like keeping cool under pressure, following procedure, interpreting chaotic information, etc. are.

Ok, you've hired William because he's got 20/20 and full colour vision.

One problem: William's in the toilet. He had a bad taco for lunch and honestly, he's going to be in there for a good 10 minutes. And there's a missile coming. Luckily Frank the IT guy is there and knows what to do but ... he's colourblind!

Oh dear. He's just sent out a dummy warning by mistake and now half of Hawaii is going to die. Well done.