Twenty Seventeen: Consider making panel border dashes and notices more WP colors

[karmatosed]

This also will only need to be looked into if we have the theme based multi-panel, but it's worth considering. Currently we have this for the dashes and labels:

I would first like to understand why they are purple, there may be something I'm missing. If there is no set reason, then I'd like to suggest we bring them more into WP and base on those colors.

[karmatosed]

Marked as 'dev-feedback' due to the discussion over on the GitHub ticket: ​https://github.com/WordPress/twentyseventeen/issues/224. I moved it here as part of merge.

[celloexpressions]

I was thinking we'd use #38399 for this; don't want the conversation to become too fragmented but we could discuss here as well.

[celloexpressions]

Fist pass.

[celloexpressions]

38408.0.diff​ is a first pass to match the visible edit shortcut colors. For some reason the z-index: -1 no longer seems to work here - the border is hidden. Need to fix that but can't change the z-index because the section content needs to be accessible so you can click through links to posts, etc.

[melchoyce]

Thanks @celloexpressions. Can you add some screenshots?

[celloexpressions]

With patch, note that the border aren't actually shown when editing colors.

[celloexpressions]

Fix border visibility after header videos.

[celloexpressions]

38408.1.diff​ also fixes the visibility of the borders after the header videos commit. See screencast above, but keep in mind that you won't see then changing while you change your selected color hue, that's just for demo purposes.

[davidakennedy]

In 38988:

Twenty Seventeen: Make border colors for panels match WordPress UI

Also, fixes the visibility of the borders for panels after the header videos commit.

Props celloexpressions.

Fixes #38408.
See #38172.