Customizer: Accessibility: color contrast ratio is poor

[designsimply]

/hat tip @afercia for the original report at ​https://github.com/voldemortensen/menu-customizer/issues/98

Spotted some light greys on light backgrounds which are under the minimum contrast ratio, for example #999 on #fff in .theme-location-set or current menu location is #999 on #eee. Some of them come from core CSS files.

[designsimply]

Noting a comment from @celloexpressions on the original issue:

We'll need to alter the design intent of the current colors quite a bit to make them meet the contrast guidelines, and they're almost all core colors.

[designsimply]

Screenshot for reference:

^{Tested with WordPress 4.3-alpha-32775 and Menu Customizer plugin 0.6 (cef7fbc).}

[designsimply]

Duplicate of #32679.

[celloexpressions]

Fix inadequate text color contrast issues.

[celloexpressions]

This isn't a duplicate - other ticket is about contrast for boxes (regarding borders, backgrounds, etc.), whereas this is about text colors. 32727.diff​ should do it with the exception of icons that don't meet contrast guidelines (and can't really without changing the design intent more significantly). Note that these changes reduce the visual hierarchy between different pieces of text, but that there's no way around that here.

[celloexpressions]

Should be ready for commit.

[SergeyBiryukov]

In 32982:

Customizer: Increase color contrast ratio for menu locations text.

props celloexpressions.
fixes #32727.