Feature request: Add customizable icon/mascot color theme

Currently the Claude Code mascot icon is orange. It would be great to have the ability to customize the icon color, particularly to change it to green.

This could be implemented as:

• A configuration option in the Claude Code settings
• Support for theme customization (dark mode, light mode, custom colors, etc.)
• An environment variable to override the default icon color

The ability to customize the visual appearance would make Claude Code feel more personalized and integrated with different user preferences and workflows.