Twenty Nineteen: .button doesn't override link color

[laurelfulford]

Originally reported by @crunnells in Twenty Nineteen's GitHub repo:

I noticed this one ​the theme demo site when I tried to change the "Get in touch" button into a link. If you put a link inside of an element with the .button class, the link color is the same color blue as the background, so the text can't be read. The same thing occurs when you try <a href="#" class="button">, so we'll need to have an override on the link color so that it's readable.

Moved over from: ​https://github.com/WordPress/twentynineteen/issues/746

[laurelfulford]

Twenty Nineteen - links with the class .button

[laurelfulford]

Twenty Nineteen - visited link with the class .button

[laurelfulford]

I could recreate this in the widget area, when non-visited links had the .button class added. The theme's .widget a styles is overriding the white text colour on the .button class.

:visited links display correctly initially. Both :visited and non-visited links display low contrast on hover (blue text on a black background).

[poena]

Since the widget area is now block-based, I think this could be solved with https://core.trac.wordpress.org/ticket/60408

-Because the theme design for the button block is the same as an element with the custom .button class.