Payments → Overview link/highlight colours are inconsistent for users with a custom admin theme enabled

[Jinksi]

Describe the bug

For users who have a custom WP admin theme enabled, links and highlights on the Payments → Overview screen are inconsistent, with some elements using the theme highlight colour and others using a hard-coded blue colour.

It is common for users to have a custom admin theme enabled, as some WordPress themes introduce additional admin themes that may be selected by default for users.

For example, WPCOM-hosted sites have custom admin themes available, including "Classic Dark" which was the default WooExpress theme, with magenta highlights.

Screenshots

To Reproduce

1. In WP Admin, navigate to Users → Profile
2. Select a different admin theme
   
3. Navigate to Payments → Overview
4. Notice that some links are coloured blue, while some match the admin theme colours.

Expected behavior

Links and highlights should use custom theme colours.

Additional context

Discussed in PR #9571

[Jinksi]

Assigning this with focus: deposits and focus: reporting since most/all of the problematic links are within related cards on the overview screen.

[haszari]

Shifting this back to In progress while we're waiting on input from design.