Encourage use of icons with form validation states for the sake of colorblind users?

[cvrebert]

Refs #14744. Perhaps we should add a note to the form field validation state docs warning about their accessibility to colorblind users, and recommending the additional use of the indicator icons for the sake of such users? What do you think @patrickhlauke?

[kkirsche]

I'm very much for this.

Normal:

Protanopia / Dueteranopia (Red / Green Color Blindness):

Image generated using Adobe Photoshop Color Blind Preview

[patrickhlauke]

Commented on #15929 but in principle, even inputs/checkboxes/etc with an explicit bit of text (e.g. a bit of text saying "error"/"invalid"/etc or something as part of the label) would be nominally accessible to colorblind users (i.e. icons are not the only way to help this user group). In principle, I'm all for expanding the note, as per #15929, as long as we don't give the impression that only icons are the way to go.

[cvrebert]

even inputs/checkboxes/etc with an explicit bit of text (e.g. a bit of text saying "error"/"invalid"/etc or something as part of the label) would be nominally accessible to colorblind users

Ah, true. However, none of the existing examples clearly do that.
Also I think a lot of folks prefer to put that text in the help text (a la formvalidation.io) rather than the <label>.

[patrickhlauke]

the help text approach is also valid for colorblind users, mind (and because of the aria-describedby for AT users too). but yes, i think #15929 is on the right track, just needs a tiny bit of tweaking of the wording