Code snippets in assistant responses rendered with diff-like red/green color scheme

Description

When Claude Code displays code snippets in assistant responses (e.g. during plan presentation or general replies), the syntax highlighting uses a red/green/white color scheme that closely resembles a diff view. This is misleading because these snippets are not diffs — they are plain code blocks.

Key distinction: this is not about the diff viewer (used when viewing file edits). This is about syntax-highlighted code blocks embedded in assistant text responses/plans, which should have no semantic association with additions or removals.

Steps to reproduce

1. Ask Claude to plan or explain something that involves code snippets.
2. Observe the syntax highlighting applied to the code blocks in the response.

Expected behavior

Code blocks in assistant responses should use a color scheme that does not resemble diff output (i.e. avoid red/green as primary highlight colors for non-diff content).

Actual behavior

Code blocks are highlighted with red, green, and white — visually indistinguishable from a diff, causing confusion about whether lines represent additions/removals. See attached screenshot from part of a plan output:

<img width="1759" height="528" alt="Image" src="https://github.com/user-attachments/assets/14afa8bb-fcbd-4721-a02f-30bd383f363c" />

Additional context

• Occurs across all available themes (dark, light, dark-daltonized, light-daltonized).
• There is currently no setting to decouple code block syntax highlighting colors from diff colors.