About 10% of the male population has some form of colour blindness, which is a fairly large percentage. Letting the market make decisions only leads to discriminatory practices. Worse, these practices can have an impact upon a person's life. For example: it can, and already does, affect employability.
Also keep in mind features that address a disability can be of benefit to everyone. For example: being able to identify something by shape can be useful to the colour blind, blind, and sighted people.
You say that but, and I realise it's pedantic, your comment only supports not limiting the identification to only coloured rings.
Coloured rings would be a very good solution for a large percentage of the users. Glyphs will also fail with the blind, maybe with dyslexics.
Or of interest, would you pay more for glyph coded versions? Just pondering if The Market would ever create a solution.