[FEATURE] Option to customize user input message colors

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Add an option to customize the color or styling of user input messages in the chat interface, making them visually distinct from Claude's responses.

Proposed Solution

• A color/style option in /theme for user messages
• Or a config setting like userMessageColor or userMessageStyle

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Configuration and settings

Use Case Example

1. I start a Claude Code session to brainstorm features for my project
2. Over 20+ exchanges, Claude and I discuss various implementation ideas - authentication approaches, database schemas, API design, etc.
3. Later in the session, I want to revisit an idea I mentioned earlier about caching
4. I scroll up through the conversation to find where I originally brought it up
5. Problem: The conversation is a wall of text where my messages and Claude's responses visually blend together. I have to carefully read through to distinguish who said what.
6. Desired: My messages would have a distinct color (e.g., a subtle highlight or different text color), allowing me to quickly scan and spot my own inputs while scrolling

Additional Context

This would be especially helpful for longer planning/brainstorming sessions where users need to reference earlier parts of the conversation.