Feature request: configurable diff highlighting colors on MCP tool results

Problem

MCP tool results display with hardcoded true-color red/green diff-style background highlighting. On dark terminal themes, the red background is visually aggressive and distracting. There is no way to configure, mute, or disable this highlighting.

Request

Add a setting (e.g. in ~/.claude/settings.json) to control tool result diff highlighting. Options could include:

• Disable diff highlighting entirely
• Switch to a muted/subtle palette
• Respect the terminal's ANSI color palette instead of hardcoded RGB values
• A theme option (light/dark/muted)

Context

• The collapsed JSON view of MCP results uses red background for response values and green/teal for parameters
• On dark backgrounds, the saturated red is particularly harsh
• NO_COLOR=1 does not affect this (ref: #8561)
• Related: #14144

Environment

• Claude Code v2.1.44
• macOS Terminal.app, dark theme
• tmux