The add block button in the edit mode on the navigation layout page has a too low color contrast

Problem/Motivation

If you switch on the edit mode on admin/config/user-interface/navigation-block the button in light mode has a too low color contrast:

#eff6fc against the background in white (#fff) that leads to a color contrast of 1.1:1 the minimum required contrast is at 3:1

in dark mode the design is broken ( 🐛 The design is broken on the navigation layout page in dark mode Active ) therefore i am not sure which color would have be chosen as the button background color.

the button is also missing a style change on hover or on click. only the button label gets a style change on hover or click

Steps to reproduce

• go to admin/config/user-interface/navigation-block
• enable the edit mode

Proposed resolution

increase the color contrast for the button / action link and apply style changes not only to the button label but the entire button on hover or click

Remaining tasks

User interface changes

API changes

Data model changes