Events and News dashboard widget: improve the color contrast

[afercia]

In the Events and News dashboard widget, all the gray text in the area highlighted in the screenshot below is currently #72777c on a very light gray background #fafafa.

This colors combination has a contrast ratio of 4.33:1 while it should be at least 4.5:1, see
​https://jdlsn.com/color/?type=hex&color=72777c&color2=fafafa

The text should use a slightly darker gray. Among the grays in the current official color palette, the one to use is "DARK GRAY 400" #606A73.

WordPress color palette references:

• ​https://make.wordpress.org/design/handbook/design-guide/foundations/colors/
• ​https://codepen.io/hugobaeta/full/RNOzoV/

See also #40633

[boemedia]

I've made the changes in the corresponding css-file. However, at the moment I'm lost in the magical mystical world of how to create a patch. Once I've figured it out, I'll upload the patch to this ticket.

[boemedia]

It seems like I finally managed to create a working patch. It's my first one, so if anyone is willing to test it, I'd be really happy :)

[lucagrandicelli]

Actually, i think a darker gray is way better. The original colour (#72777c) is the same of the rapid draft input placeholders, which obviously have not the same relevance of an event date. I suggest Dark Gray 800: #23282d

[afercia]

Let's go for something in between: #32373c is the "base gray", already used for text in several other cases.

[afercia]

In 44549:

Accessibility: Improve color contrast ratio in the Events and News dashboard widget.

Props boemedia, lucagrandicelli.
Fixes #45280.