frontend: Fix monitoring icon color

[shiina424]

Description

This fixes an issue where the monitoring icon color did not change correctly.
With this change, the icon color now matches the color used in other themes.

Before (Acri)

before-Acri.mp4

After (Acri)

after-Acri.mp4

Before (Rachni)

before-Rachni.mp4

After (Rachni)

after-Rachni.mp4

This is the best I could do with my current knowledge.
If you see a better approach, please feel free to update or close this PR.

Motivation and Context

In the Acri and Rachni themes, the monitoring icon color did not change, making it difficult to determine the current monitoring state.

How Has This Been Tested?

Tested on Windows 11 25H2 using a local build.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.