Adding --colors option

src/cli.rs

@@ -316,6 +316,10 @@ enum Commands {
         #[arg(long, short = 'n', conflicts_with = "session")]
         new: bool,
 
+        /// Apply per-window color tinting (tmux only)
+        #[arg(long)]
+        colors: bool,
+
         /// Open in session mode (overrides stored mode for this worktree)
         #[arg(short = 's', long)]
         session: bool,
@@ -722,9 +726,10 @@ pub fn run() -> Result<()> {
             run_hooks,
             force_files,
             new,
+            colors,
             session,
             prompt,
-        } => command::open::run(&names, run_hooks, force_files, new, session, prompt),
+        } => command::open::run(&names, run_hooks, force_files, new, colors, session, prompt),
         Commands::Close { name } => command::close::run(name.as_deref()),
         Commands::Merge {
             name,

src/command/add.rs

@@ -162,8 +162,9 @@ pub fn run(
     // Ensure preconditions are met (git repo and multiplexer session)
     check_preconditions()?;
 
-    // Extract sandbox override before consuming setup flags
+    // Extract overrides before consuming setup flags
     let sandbox_override = setup.sandbox;
+    let colors_override = setup.colors;
 
     // Load config early to determine mode (CLI flag overrides config)
     let initial_config = config::Config::load(multi.agent.first().map(|s| s.as_str()))?;
@@ -288,6 +289,9 @@ pub fn run(
         if sandbox_override {
             rescue_config.sandbox.enabled = Some(true);
         }
+        if colors_override {
+            rescue_config.window_colors = Some(true);
+        }
         let mux = create_backend(detect_backend());
         let rescue_context = workflow::WorkflowContext::new(rescue_config, mux, rescue_location)?;
         // Derive handle for rescue flow (uses config for naming strategy/prefix)
@@ -414,6 +418,7 @@ pub fn run(
         deferred_auto_name,
         max_concurrent: multi.max_concurrent,
         sandbox_override,
+        colors_override,
         prompt_file_only,
     };
     plan.execute()
@@ -543,6 +548,7 @@ struct CreationPlan<'a> {
     deferred_auto_name: bool,
     max_concurrent: Option<u32>,
     sandbox_override: bool,
+    colors_override: bool,
     prompt_file_only: bool,
 }
 
@@ -593,6 +599,9 @@ impl<'a> CreationPlan<'a> {
             if self.sandbox_override {
                 config.sandbox.enabled = Some(true);
             }
+            if self.colors_override {
+                config.window_colors = Some(true);
+            }
 
             // Render prompt first (needed for deferred auto-name)
             let rendered_prompt = if let Some(doc) = self.prompt_doc {

src/command/args.rs

@@ -58,6 +58,10 @@ pub struct SetupFlags {
     /// Enable sandbox mode even when disabled in config
     #[arg(short = 'S', long)]
     pub sandbox: bool,
+
+    /// Apply per-window color tinting (tmux only)
+    #[arg(long)]
+    pub colors: bool,
 }
 
 #[derive(clap::Args, Debug)]

src/command/open.rs

@@ -11,6 +11,7 @@ pub fn run(
     run_hooks: bool,
     force_files: bool,
     new_window: bool,
+    colors: bool,
     session: bool,
     prompt_args: PromptArgs,
 ) -> Result<()> {
@@ -33,7 +34,10 @@ pub fn run(
         bail!("Prompt arguments (-p, -P, -e) cannot be used when opening multiple worktrees");
     }
 
-    let (config, config_location) = config::Config::load_with_location(None)?;
+    let (mut config, config_location) = config::Config::load_with_location(None)?;
+    if colors {
+        config.window_colors = Some(true);
+    }
     let mux = create_backend(detect_backend());
     let context = WorkflowContext::new(config, mux, config_location)?;
 

src/config.rs

@@ -193,6 +193,12 @@ pub struct Config {
     #[serde(default)]
     pub status_format: Option<bool>,
 
+    /// Apply subtle background color tinting per window (tmux only).
+    /// Colors are derived from the branch name for consistent identification.
+    /// Default: false
+    #[serde(default)]
+    pub window_colors: Option<bool>,
+
     /// Custom icons for agent status display.
     #[serde(default)]
     pub status_icons: StatusIcons,
@@ -1504,6 +1510,7 @@ impl Config {
             panes,
             windows,
             status_format,
+            window_colors,
             nerdfont,
             auto_update_check,
             prompt_file_only,
@@ -1904,6 +1911,11 @@ pub const EXAMPLE_PROJECT_CONFIG: &str = r#"# workmux project configuration
 # Default: true
 # status_format: true
 
+# Apply subtle background color tinting per window (tmux only).
+# Colors are derived from the branch name for consistent identification.
+# Default: false
+# window_colors: true
+
 # Custom icons for agent status display.
 # status_icons:
 #   working: "🤖"

src/multiplexer/mod.rs

@@ -158,6 +158,13 @@ pub trait Multiplexer: Send + Sync {
     /// Wait until the specified session is closed
     fn wait_until_session_closed(&self, full_session_name: &str) -> Result<()>;
 
+    /// Apply a background color tint to a window based on a name hash.
+    /// Colors are derived from the name for consistent identification.
+    /// Only supported by tmux backend. Other backends silently ignore this.
+    fn apply_window_color(&self, _pane_id: &str, _name: &str) -> Result<()> {
+        Ok(())
+    }
+
     // === Pane Management ===
 
     /// Select (focus) a pane by ID

src/multiplexer/tmux.rs

@@ -556,6 +556,30 @@ impl Multiplexer for TmuxBackend {
         }
     }
 
+    fn apply_window_color(&self, pane_id: &str, name: &str) -> Result<()> {
+        let scheme = window_color_for_name(name);
+        // Pane content: background and text color
+        let pane_style = format!("bg={},fg={}", scheme.bg, scheme.fg);
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "window-style", &pane_style])?;
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "window-active-style", &pane_style])?;
+        // Pane borders
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "pane-border-style", &format!("fg={}", scheme.border)])?;
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "pane-active-border-style", &format!("fg={}", scheme.active_border)])?;
+        // Status bar: this window's tab in the bottom bar
+        let tab_style = format!("bg={},fg={}", scheme.status_bg, scheme.status_fg);
+        let active_tab_style = format!("bg={},fg={},bold", scheme.active_border, scheme.status_fg);
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "window-status-style", &tab_style])?;
+        self.tmux_cmd(&["set-option", "-w", "-t", pane_id, "window-status-current-style", &active_tab_style])?;
+        // Status bar background: update the session-level status-style when this window is focused.
+        // Uses hook index [99] to avoid conflicting with other pane-focus-in hooks.
+        let status_bar_style = format!("bg={},fg={}", scheme.status_bg, scheme.status_fg);
+        let hook_cmd = format!("set-option status-style '{}'", status_bar_style);
+        let _ = self.tmux_cmd(&["set-hook", "-w", "-t", pane_id, "pane-focus-in[99]", &hook_cmd]);
+        // Apply immediately for the current window
+        self.tmux_cmd(&["set-option", "-t", pane_id, "status-style", &status_bar_style])?;
+        Ok(())
+    }
+
     // === Pane Management ===
 
     fn select_pane(&self, pane_id: &str) -> Result<()> {
@@ -796,6 +820,51 @@ impl Multiplexer for TmuxBackend {
         Ok(panes)
     }
 }
+
+/// A complete color scheme for a tmux window: background, text, borders, and status bar.
+struct WindowColorScheme {
+    /// Subtle background tint
+    bg: &'static str,
+    /// Text color (light, complementary to background hue)
+    fg: &'static str,
+    /// Pane border color (muted accent)
+    border: &'static str,
+    /// Active pane border color (brighter accent)
+    active_border: &'static str,
+    /// Status bar tab background for this window
+    status_bg: &'static str,
+    /// Status bar tab text color for this window
+    status_fg: &'static str,
+}
+
+/// Palette of 12 color schemes for per-window tinting.
+/// Each scheme uses a tinted dark background with coordinated text, border, and status bar colors.
+const WINDOW_COLOR_PALETTE: &[WindowColorScheme] = &[
+    WindowColorScheme { bg: "#141430", fg: "#b8b8d0", border: "#3a3a5e", active_border: "#6868b0", status_bg: "#1e1e48", status_fg: "#c8c8e0" }, // blue
+    WindowColorScheme { bg: "#143014", fg: "#b8d0b8", border: "#3a5e3a", active_border: "#68b068", status_bg: "#1e481e", status_fg: "#c8e0c8" }, // green
+    WindowColorScheme { bg: "#301414", fg: "#d0b8b8", border: "#5e3a3a", active_border: "#b06868", status_bg: "#481e1e", status_fg: "#e0c8c8" }, // red
+    WindowColorScheme { bg: "#143030", fg: "#b8d0d0", border: "#3a5e5e", active_border: "#68b0b0", status_bg: "#1e4848", status_fg: "#c8e0e0" }, // cyan
+    WindowColorScheme { bg: "#303014", fg: "#d0d0b8", border: "#5e5e3a", active_border: "#b0b068", status_bg: "#48481e", status_fg: "#e0e0c8" }, // yellow
+    WindowColorScheme { bg: "#301430", fg: "#d0b8d0", border: "#5e3a5e", active_border: "#b068b0", status_bg: "#481e48", status_fg: "#e0c8e0" }, // magenta
+    WindowColorScheme { bg: "#141a28", fg: "#b8c0c8", border: "#3a4858", active_border: "#6878a0", status_bg: "#1e2840", status_fg: "#c8d0d8" }, // slate
+    WindowColorScheme { bg: "#281a14", fg: "#c8c0b8", border: "#58483a", active_border: "#a07868", status_bg: "#40281e", status_fg: "#d8d0c8" }, // warm
+    WindowColorScheme { bg: "#142818", fg: "#b8c8c0", border: "#3a5848", active_border: "#68a078", status_bg: "#1e4028", status_fg: "#c8d8d0" }, // forest
+    WindowColorScheme { bg: "#1a1428", fg: "#c0b8c8", border: "#483a58", active_border: "#7868a0", status_bg: "#281e40", status_fg: "#d0c8d8" }, // purple
+    WindowColorScheme { bg: "#282814", fg: "#c8c8b8", border: "#58583a", active_border: "#a0a068", status_bg: "#40401e", status_fg: "#d8d8c8" }, // olive
+    WindowColorScheme { bg: "#141c24", fg: "#b8c0c5", border: "#3a4850", active_border: "#688090", status_bg: "#1e2c38", status_fg: "#c8d0d5" }, // steel
+];
+
+/// Derive a deterministic palette color scheme from a name string.
+/// Uses FNV-1a hash for fast, well-distributed mapping.
+fn window_color_for_name(name: &str) -> &'static WindowColorScheme {
+    let mut hash: u64 = 0xcbf29ce484222325; // FNV offset basis
+    for byte in name.as_bytes() {
+        hash ^= *byte as u64;
+        hash = hash.wrapping_mul(0x100000001b3); // FNV prime
+    }
+    &WINDOW_COLOR_PALETTE[(hash as usize) % WINDOW_COLOR_PALETTE.len()]
+}
+
 /// Format string to inject into tmux window-status-format.
 const WORKMUX_STATUS_FORMAT: &str = "#{?@workmux_status, #{@workmux_status},}";
 
@@ -875,4 +944,45 @@ mod tests {
             " #I:#W#{?@workmux_status, #{@workmux_status},}#{window_flags} "
         );
     }
+
+    #[test]
+    fn test_window_color_deterministic() {
+        // Same name always produces the same color scheme
+        let scheme1 = window_color_for_name("feature-auth");
+        let scheme2 = window_color_for_name("feature-auth");
+        assert_eq!(scheme1.bg, scheme2.bg);
+        assert_eq!(scheme1.fg, scheme2.fg);
+        assert_eq!(scheme1.border, scheme2.border);
+        assert_eq!(scheme1.active_border, scheme2.active_border);
+    }
+
+    #[test]
+    fn test_window_color_different_names() {
+        // Different names should (very likely) produce different schemes
+        let scheme1 = window_color_for_name("feature-auth");
+        let scheme2 = window_color_for_name("fix-bug-123");
+        let scheme3 = window_color_for_name("refactor-db");
+        // At least 2 of 3 should differ
+        assert!(scheme1.bg != scheme2.bg || scheme2.bg != scheme3.bg);
+    }
+
+    #[test]
+    fn test_window_color_scheme_has_all_fields() {
+        // Every name produces a scheme with non-empty hex color values
+        for name in &["main", "develop", "feature-x", "hotfix-y", "a", ""] {
+            let scheme = window_color_for_name(name);
+            let fields = [
+                ("bg", scheme.bg),
+                ("fg", scheme.fg),
+                ("border", scheme.border),
+                ("active_border", scheme.active_border),
+                ("status_bg", scheme.status_bg),
+                ("status_fg", scheme.status_fg),
+            ];
+            for (field, value) in &fields {
+                assert!(!value.is_empty(), "{} empty for '{}'", field, name);
+                assert!(value.starts_with('#'), "{} not hex for '{}'", field, name);
+            }
+        }
+    }
 }

src/workflow/setup.rs

@@ -183,6 +183,10 @@ pub fn setup_environment(
                 "setup_environment:window created"
             );
 
+            if config.window_colors.unwrap_or(false) {
+                let _ = mux.apply_window_color(&initial_pane_id, handle);
+            }
+
             let result = mux
                 .setup_panes(
                     &initial_pane_id,
@@ -241,6 +245,10 @@ pub fn setup_environment(
                     pane_id
                 };
 
+                if config.window_colors.unwrap_or(false) {
+                    let _ = mux.apply_window_color(&initial_pane_id, handle);
+                }
+
                 let result = mux
                     .setup_panes(
                         &initial_pane_id,