Fix LinkLabel contrast in Dark Mode

[LeafShi1]

Fixes #11935

Proposed changes

• LinkColor (normal link state):

  • Dark Mode: Color.FromArgb(102, 178, 255) - A bright blue that contrasts well with dark backgrounds

• ActiveLinkColor (when link is being clicked):

  • Dark Mode: Color.FromArgb(255, 128, 128) - Light red color for clear visual feedback

• VisitedLinkColor (after link has been visited):

  • Dark Mode: Uses Color.FromArgb(200, 162, 255) - Light purple color for a visible visited state

Customer Impact

• The LinkLabel can be displayed clearly in DarkMode

Regression?

• No

Risk

• Minimal

Screenshots

Before

BeforeChanges.mp4

After

AfterChanges.mp4

Test methodology

• Manually

Test environment(s)

• .net 11.0.0-preview.2.26080.101

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.18743%. Comparing base (9b546b7) to head (d67d48a).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14283         +/-   ##
===================================================
+ Coverage   77.18395%   77.18743%   +0.00348%     
===================================================
  Files           3279        3279                 
  Lines         645138      645153         +15     
  Branches       47730       47730                 
===================================================
+ Hits          497943      497977         +34     
+ Misses        143503      143487         -16     
+ Partials        3692        3689          -3     

Flag	Coverage Δ
Debug	77.18743% <72.72727%> (+0.00348%)	⬆️
integration	19.00673% <45.45455%> (+0.01609%)	⬆️
production	52.07229% <72.72727%> (+0.00910%)	⬆️
test	97.40479% <ø> (ø)
unit	49.49622% <72.72727%> (-0.00640%)	⬇️

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Pull request overview

Updates LinkLabel’s default link colors when Dark Mode is enabled to improve contrast and align with the reported usability issue (#11935).

Changes:

• Adjust LinkColor default in Dark Mode to a brighter blue for better readability.
• Adjust ActiveLinkColor default in Dark Mode to a red tone for clearer click/active feedback.
• Update VisitedLinkColor default selection logic to use LinkUtilities.GetVisitedLinkColor() when Dark Mode is enabled.