Improve the "dismiss notice" button color contrast

[afercia]

Most of the notices in the admin have a "Dismiss notice" button. Other UI components use similar buttons, for example the media views when there is an upload error (see screenshots below).

These buttons color contrast ratio is too low for accessibility. It would be great to improve it to get a contrast ratio of at least 4.5:1. On a white background, the #72777c WordPress grey would make it.

Example: the dismiss notice button when updating a post:

Also, it could be a good opportunity to fix an edge case in the media modal. When adding media from the edit post screen and there's an upload error, no "dismiss errors" button gets displayed. However, the button is there and is functional. It's just completely unstyled:

While it's not visible, it can still be focused and activated when using a keyboard or a screen reader. Not sure it this is intentional, but I'd say if this control isn't essential in this context, then it should be completely hidden from all users. Otherwise, it should be styled.

Worth noting the same button in the Media Library grid has a proper styling:

[afercia]

Discussed in today's a11y bug-scrub and seems an easy fix, perfect candidate for a contributor day :)

[chris_dev]

Media screen

[chris_dev]

post/page update screen

[chris_dev]

Media sidebard screen

[chris_dev]

Hi @afercia ,

I made changes. Is it what you meant?

[afercia]

@chris_dev yes, thanks!

[rianrietveld]

Hey @chris_dev, thanks for the patch.
Tested this patch at the contributor day at WordCamp London and it work good for all the cases described by @afrecia.

Just one thing: although the colour in .notice-dismiss is overruled by .notice-dismiss:before, we think that the colour #b4b9be in .notice-dismiss should also be changed into #72777c in case the class will be used in other cases without the :before.

.notice-dismiss {
	position: absolute;
	top: 0;
	right: 1px;
	border: none;
	margin: 0;
	padding: 9px;
	background: none;
	color: #b4b9be;
	cursor: pointer;
}

Maybe it's useful to investigate if there are more cases where #b4b9be is used.

[chris_dev]

Hi @rianrietveld ,

Thank you for the comments, I'll investigate all stylesheets whether that colour is used or not ant let you know.

[chris_dev]

Hi @rianrietveld ,

I searched all files and found one more it in wp-pointer.css

I added new patch.

[afercia]

Refreshed patch to apply cleanly from the root. Also adds hover/focus style for the media upload "dismiss error" button.

[afercia]

In 40570:

Accessibility: Improve the color contrast ratio of the dismiss notice buttons.

Props chris_dev.
Fixes #39970.

[chris_dev]

Cheers~