[FEATURE] persist session color (/color) across sessions via settings.json

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

Summary

The /color command sets a session color for the UI, but this setting is lost when the session ends. There is no way to persist it via settings.json.

Current behavior

Running /color orange applies the color only for the current session. On the next session, the color resets to the default.

Expected behavior

A color field in settings.json that persists the chosen color across sessions:

{
  "color": "orange"
}

Workaround attempted

Tried using a SessionStart hook to invoke /color, but hooks only execute shell commands — slash commands are not supported in that context.

Why this matters

Users who prefer a specific color for visual identification (e.g., to distinguish between multiple Claude Code sessions or projects) have to re-apply the color manually every session.

### Proposed Solution

## Proposed solution

Read the `color` field from `settings.json` at session startup and apply it automatically, equivalent to running `/color <value>` as the first action of the session. This would require:

1. Adding `color` as a recognized field in the settings schema.
2. Applying the color during session initialization, before the first prompt is shown.

Alternatively, a `SessionStart` hook could support a `color` key in its JSON output:

```json
{ "color": "orange" }

This would allow dynamic color selection (e.g., per-project color via .claude/settings.json) without requiring a new top-level schema field.

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Configuration and settings

Use Case Example

_No response_

Additional Context

_No response_