DRYD-1299: Update color to meet expected contrast ratio

[mikejritter]

What does this do?

• Updates the color of active navlink elements to meet the expected contrast ratio

Why are we doing this? (with JIRA link)
Jira: https://collectionspace.atlassian.net/browse/DRYD-1299

This is part of the wcag audit, and is to fix the contrast ratio for active nav link elements.

How should this be tested? Do these changes have associated tests?

• Run the devserver and navigate using the nav bar
• Observe that the active element has a contrast ratio of at least 4.5:1

Dependencies for merging? Releasing to production?
None, though I'm wondering if there's a way to check some of the accessibility updates in the test suite. Seems like it would be nice to have, though not strictly necessary.

Has the application documentation been updated for these changes?
No

Did someone actually run this code to verify it works?
@mikejritter tested locally

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (90c22fe) 95.47% compared to head (fcb5ca9) 95.47%.
Report is 3 commits behind head on master.

❗ Current head fcb5ca9 differs from pull request most recent head cf38d05. Consider uploading reports for the commit cf38d05 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #198   +/-   ##
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  Coverage   95.47%   95.47%           
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  Files         555      555           
  Lines       10899    10899           
  Branches     1196     1196           
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  Hits        10406    10406           
  Misses        147      147           
  Partials      346      346           

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