[EuiHeader][COLOR CONTRAST]: Header breadcrumbs with blue background have color contrast ratio below 4.5:1

[Trevor Pierce]

Describe the problem

While auditing some Kibana items, I discovered a recurring color contrast issue in the heading breadcrumbs. I traced it to the EuiHeader component, specifically the blue breadcrumb links on the light blue background.

The breadcrumbs have a 4.17:1 ratio in the light mode and 4.35:1 ratio in dark mode. I think the issue could be remediated by adjusting the breadcrumbs to use the same color / background color as the secondary action EuiButton. Screenshots attached below.

To Reproduce

1. Navigate to EuiHeader view in EUI docs site
2. Run axe browser scan from Chrome or Firefox dev tools
3. Verify there are 6 color contrast errors, all stemming from the breadcrumbs on the page

WCAG or Vendor Guidance (optional)

• SC 1.4.3: Contast (Minimum)(Level AA)

Screenshots or Trace Logs

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[Trevor Pierce]

Thank you for clearing this issue @mgadewoll! It'll be a big improvement on the automated a11y front.