[Offline app] Music icon visibility issue in Dark and High Contrast mode on Mac platform

[Nina-1210]

Describe the bug
The music icon becomes difficult to see in Dark Mode or High Contrast Mode on macOS.

Steps to reproduce the behavior:
1.Download the Micro:bit offline app from: https://makecode.com/api/release/microbit/v8.0.12/macarm64
2.Set the theme to Dark or High Contrast.
3.Open "Rock Paper Scissors" blocks tutorial under Games section.
4.Goes to steps 16 and observe the music icons.

Actual behavior
The music icons are hard to see in Dark and High Contrast mode on Mac platform.

Expected behavior
The music icon should remain clearly visible in Dark and High Contrast mode on Mac platform.

Screenshots

Additional context
1.OS: Mac Mini M2 macOS Sequoia 15.5
2.Makecode.microbit.org version: 8.0.12
3.Microsoft MakeCode version: 12.0.12