Fix color contrast for Colored Button example.

[Nitin-100]

Description

Fixes color contrast issue on the "Colored Button" example in the Button page by changing from SystemBaseLowColor to SystemAccentColor.

Why

The "Colored Button" example was using PlatformColor('SystemBaseLowColor') which resulted in a contrast ratio of 3.56:1 - below the minimum required 4.5:1 for normal text. This made the button label difficult to read for users with low vision or contrast sensitivity.

What

• src/examples/ButtonExamplePage.tsx: Changed button color from SystemBaseLowColor to SystemAccentColor

Screenshot

Before

After

Testing

1. Open the application
2. Navigate to 'Button' page
3. Check the "Colored Button" example
4. Verify text contrast ratio meets 4.5:1 minimum

Microsoft Reviewers: Open in CodeFlow