Feature Request: Customizable colors/background for user input vs AI output

Summary

Allow users to configure distinct colors and/or background colors for their own input messages versus Claude's output, making it easier to visually distinguish the two in long conversations.

Problem

During extended coding sessions, the conversation in the terminal grows long. Both user input and Claude's output use similar styling, making it hard to quickly scan and locate my own messages versus Claude's responses. This slows down navigation and reduces readability.

Proposed Solution

Add a configuration option (e.g., via /config or settings.json) to customize:

• User input text color / background color
• Claude output text color / background color

Example config:

{
  "theme": {
    "userInput": {
      "textColor": "#e0e0e0",
      "backgroundColor": "#1a1a2e"
    },
    "assistantOutput": {
      "textColor": "#ffffff",
      "backgroundColor": "#16213e"
    }
  }
}

Alternatively, even a simple toggle for a subtle background tint on user input blocks would be a big improvement.

Why This Matters

• Improves readability in long multi-turn sessions
• Helps users quickly scan conversation history
• Common pattern in chat UIs (Slack, Discord, ChatGPT web) that terminal users would benefit from too
• Low-cost UX improvement with high impact

Additional Context

Terminal emulators control base colors but cannot differentiate between user input and AI output blocks within the same application. This needs to be handled at the Claude Code application level using ANSI escape codes.